Builtin git-read-tree.

Signed-off-by: Peter Eriksen <s022018@student.dtu.dk>
Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/Makefile b/Makefile
index a3164f8ef0444173ff16bcd951200664634aff0b..1aebcf59783aefc6ad92403b353133ed12206275 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -157,7 +157,7 @@ PROGRAMS = \
        git-hash-object$X git-index-pack$X git-local-fetch$X \
        git-mailinfo$X git-merge-base$X \
        git-merge-index$X git-mktag$X git-mktree$X git-pack-objects$X git-patch-id$X \
-       git-peek-remote$X git-prune-packed$X git-read-tree$X \
+       git-peek-remote$X git-prune-packed$X \
        git-receive-pack$X git-rev-parse$X \
        git-send-pack$X git-show-branch$X git-shell$X \
        git-show-index$X git-ssh-fetch$X \
@@ -172,7 +172,7 @@ BUILT_INS = git-log$X git-whatchanged$X git-show$X \
        git-count-objects$X git-diff$X git-push$X \
        git-grep$X git-rev-list$X git-check-ref-format$X \
        git-init-db$X git-ls-files$X git-ls-tree$X \
-       git-tar-tree$X
+       git-tar-tree$X git-read-tree$X
 
 # what 'all' will build and 'install' will install, in gitexecdir
 ALL_PROGRAMS = $(PROGRAMS) $(SIMPLE_PROGRAMS) $(SCRIPTS)
@@ -222,7 +222,7 @@ BUILTIN_OBJS = \
        builtin-log.o builtin-help.o builtin-count.o builtin-diff.o builtin-push.o \
        builtin-grep.o builtin-rev-list.o builtin-check-ref-format.o \
        builtin-init-db.o builtin-ls-files.o builtin-ls-tree.o \
-        builtin-tar-tree.o
+        builtin-tar-tree.o builtin-read-tree.o
 
 GITLIBS = $(LIB_FILE) $(XDIFF_LIB)
 LIBS = $(GITLIBS) -lz

diff --git a/builtin-read-tree.c b/builtin-read-tree.c
new file mode 100644 (file)
index 0000000..ec40d01
--- /dev/null
+++ b/builtin-read-tree.c
@@ -0,0 +1,882 @@
+/*
+ * GIT - The information manager from hell
+ *
+ * Copyright (C) Linus Torvalds, 2005
+ */
+#define DBRT_DEBUG 1
+
+#include "cache.h"
+
+#include "object.h"
+#include "tree.h"
+#include <sys/time.h>
+#include <signal.h>
+#include "builtin.h"
+
+static int reset = 0;
+static int merge = 0;
+static int update = 0;
+static int index_only = 0;
+static int nontrivial_merge = 0;
+static int trivial_merges_only = 0;
+static int aggressive = 0;
+static int verbose_update = 0;
+static volatile int progress_update = 0;
+
+static int head_idx = -1;
+static int merge_size = 0;
+
+static struct object_list *trees = NULL;
+
+static struct cache_entry df_conflict_entry = { 
+};
+
+static struct tree_entry_list df_conflict_list = {
+       .name = NULL,
+       .next = &df_conflict_list
+};
+
+typedef int (*merge_fn_t)(struct cache_entry **src);
+
+static int entcmp(char *name1, int dir1, char *name2, int dir2)
+{
+       int len1 = strlen(name1);
+       int len2 = strlen(name2);
+       int len = len1 < len2 ? len1 : len2;
+       int ret = memcmp(name1, name2, len);
+       unsigned char c1, c2;
+       if (ret)
+               return ret;
+       c1 = name1[len];
+       c2 = name2[len];
+       if (!c1 && dir1)
+               c1 = '/';
+       if (!c2 && dir2)
+               c2 = '/';
+       ret = (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
+       if (c1 && c2 && !ret)
+               ret = len1 - len2;
+       return ret;
+}
+
+static int unpack_trees_rec(struct tree_entry_list **posns, int len,
+                           const char *base, merge_fn_t fn, int *indpos)
+{
+       int baselen = strlen(base);
+       int src_size = len + 1;
+       do {
+               int i;
+               char *first;
+               int firstdir = 0;
+               int pathlen;
+               unsigned ce_size;
+               struct tree_entry_list **subposns;
+               struct cache_entry **src;
+               int any_files = 0;
+               int any_dirs = 0;
+               char *cache_name;
+               int ce_stage;
+
+               /* Find the first name in the input. */
+
+               first = NULL;
+               cache_name = NULL;
+
+               /* Check the cache */
+               if (merge && *indpos < active_nr) {
+                       /* This is a bit tricky: */
+                       /* If the index has a subdirectory (with
+                        * contents) as the first name, it'll get a
+                        * filename like "foo/bar". But that's after
+                        * "foo", so the entry in trees will get
+                        * handled first, at which point we'll go into
+                        * "foo", and deal with "bar" from the index,
+                        * because the base will be "foo/". The only
+                        * way we can actually have "foo/bar" first of
+                        * all the things is if the trees don't
+                        * contain "foo" at all, in which case we'll
+                        * handle "foo/bar" without going into the
+                        * directory, but that's fine (and will return
+                        * an error anyway, with the added unknown
+                        * file case.
+                        */
+
+                       cache_name = active_cache[*indpos]->name;
+                       if (strlen(cache_name) > baselen &&
+                           !memcmp(cache_name, base, baselen)) {
+                               cache_name += baselen;
+                               first = cache_name;
+                       } else {
+                               cache_name = NULL;
+                       }
+               }
+
+#if DBRT_DEBUG > 1
+               if (first)
+                       printf("index %s\n", first);
+#endif
+               for (i = 0; i < len; i++) {
+                       if (!posns[i] || posns[i] == &df_conflict_list)
+                               continue;
+#if DBRT_DEBUG > 1
+                       printf("%d %s\n", i + 1, posns[i]->name);
+#endif
+                       if (!first || entcmp(first, firstdir,
+                                            posns[i]->name, 
+                                            posns[i]->directory) > 0) {
+                               first = posns[i]->name;
+                               firstdir = posns[i]->directory;
+                       }
+               }
+               /* No name means we're done */
+               if (!first)
+                       return 0;
+
+               pathlen = strlen(first);
+               ce_size = cache_entry_size(baselen + pathlen);
+
+               src = xcalloc(src_size, sizeof(struct cache_entry *));
+
+               subposns = xcalloc(len, sizeof(struct tree_list_entry *));
+
+               if (cache_name && !strcmp(cache_name, first)) {
+                       any_files = 1;
+                       src[0] = active_cache[*indpos];
+                       remove_cache_entry_at(*indpos);
+               }
+
+               for (i = 0; i < len; i++) {
+                       struct cache_entry *ce;
+
+                       if (!posns[i] ||
+                           (posns[i] != &df_conflict_list &&
+                            strcmp(first, posns[i]->name))) {
+                               continue;
+                       }
+
+                       if (posns[i] == &df_conflict_list) {
+                               src[i + merge] = &df_conflict_entry;
+                               continue;
+                       }
+
+                       if (posns[i]->directory) {
+                               any_dirs = 1;
+                               parse_tree(posns[i]->item.tree);
+                               subposns[i] = posns[i]->item.tree->entries;
+                               posns[i] = posns[i]->next;
+                               src[i + merge] = &df_conflict_entry;
+                               continue;
+                       }
+
+                       if (!merge)
+                               ce_stage = 0;
+                       else if (i + 1 < head_idx)
+                               ce_stage = 1;
+                       else if (i + 1 > head_idx)
+                               ce_stage = 3;
+                       else
+                               ce_stage = 2;
+
+                       ce = xcalloc(1, ce_size);
+                       ce->ce_mode = create_ce_mode(posns[i]->mode);
+                       ce->ce_flags = create_ce_flags(baselen + pathlen,
+                                                      ce_stage);
+                       memcpy(ce->name, base, baselen);
+                       memcpy(ce->name + baselen, first, pathlen + 1);
+
+                       any_files = 1;
+
+                       memcpy(ce->sha1, posns[i]->item.any->sha1, 20);
+                       src[i + merge] = ce;
+                       subposns[i] = &df_conflict_list;
+                       posns[i] = posns[i]->next;
+               }
+               if (any_files) {
+                       if (merge) {
+                               int ret;
+
+#if DBRT_DEBUG > 1
+                               printf("%s:\n", first);
+                               for (i = 0; i < src_size; i++) {
+                                       printf(" %d ", i);
+                                       if (src[i])
+                                               printf("%s\n", sha1_to_hex(src[i]->sha1));
+                                       else
+                                               printf("\n");
+                               }
+#endif
+                               ret = fn(src);
+                               
+#if DBRT_DEBUG > 1
+                               printf("Added %d entries\n", ret);
+#endif
+                               *indpos += ret;
+                       } else {
+                               for (i = 0; i < src_size; i++) {
+                                       if (src[i]) {
+                                               add_cache_entry(src[i], ADD_CACHE_OK_TO_ADD|ADD_CACHE_SKIP_DFCHECK);
+                                       }
+                               }
+                       }
+               }
+               if (any_dirs) {
+                       char *newbase = xmalloc(baselen + 2 + pathlen);
+                       memcpy(newbase, base, baselen);
+                       memcpy(newbase + baselen, first, pathlen);
+                       newbase[baselen + pathlen] = '/';
+                       newbase[baselen + pathlen + 1] = '\0';
+                       if (unpack_trees_rec(subposns, len, newbase, fn,
+                                            indpos))
+                               return -1;
+                       free(newbase);
+               }
+               free(subposns);
+               free(src);
+       } while (1);
+}
+
+static void reject_merge(struct cache_entry *ce)
+{
+       die("Entry '%s' would be overwritten by merge. Cannot merge.", 
+           ce->name);
+}
+
+/* Unlink the last component and attempt to remove leading
+ * directories, in case this unlink is the removal of the
+ * last entry in the directory -- empty directories are removed.
+ */
+static void unlink_entry(char *name)
+{
+       char *cp, *prev;
+
+       if (unlink(name))
+               return;
+       prev = NULL;
+       while (1) {
+               int status;
+               cp = strrchr(name, '/');
+               if (prev)
+                       *prev = '/';
+               if (!cp)
+                       break;
+
+               *cp = 0;
+               status = rmdir(name);
+               if (status) {
+                       *cp = '/';
+                       break;
+               }
+               prev = cp;
+       }
+}
+
+static void progress_interval(int signum)
+{
+       progress_update = 1;
+}
+
+static void setup_progress_signal(void)
+{
+       struct sigaction sa;
+       struct itimerval v;
+
+       memset(&sa, 0, sizeof(sa));
+       sa.sa_handler = progress_interval;
+       sigemptyset(&sa.sa_mask);
+       sa.sa_flags = SA_RESTART;
+       sigaction(SIGALRM, &sa, NULL);
+
+       v.it_interval.tv_sec = 1;
+       v.it_interval.tv_usec = 0;
+       v.it_value = v.it_interval;
+       setitimer(ITIMER_REAL, &v, NULL);
+}
+
+static void check_updates(struct cache_entry **src, int nr)
+{
+       static struct checkout state = {
+               .base_dir = "",
+               .force = 1,
+               .quiet = 1,
+               .refresh_cache = 1,
+       };
+       unsigned short mask = htons(CE_UPDATE);
+       unsigned last_percent = 200, cnt = 0, total = 0;
+
+       if (update && verbose_update) {
+               for (total = cnt = 0; cnt < nr; cnt++) {
+                       struct cache_entry *ce = src[cnt];
+                       if (!ce->ce_mode || ce->ce_flags & mask)
+                               total++;
+               }
+
+               /* Don't bother doing this for very small updates */
+               if (total < 250)
+                       total = 0;
+
+               if (total) {
+                       fprintf(stderr, "Checking files out...\n");
+                       setup_progress_signal();
+                       progress_update = 1;
+               }
+               cnt = 0;
+       }
+
+       while (nr--) {
+               struct cache_entry *ce = *src++;
+
+               if (total) {
+                       if (!ce->ce_mode || ce->ce_flags & mask) {
+                               unsigned percent;
+                               cnt++;
+                               percent = (cnt * 100) / total;
+                               if (percent != last_percent ||
+                                   progress_update) {
+                                       fprintf(stderr, "%4u%% (%u/%u) done\r",
+                                               percent, cnt, total);
+                                       last_percent = percent;
+                               }
+                       }
+               }
+               if (!ce->ce_mode) {
+                       if (update)
+                               unlink_entry(ce->name);
+                       continue;
+               }
+               if (ce->ce_flags & mask) {
+                       ce->ce_flags &= ~mask;
+                       if (update)
+                               checkout_entry(ce, &state, NULL);
+               }
+       }
+       if (total) {
+               signal(SIGALRM, SIG_IGN);
+               fputc('\n', stderr);
+       }
+}
+
+static int unpack_trees(merge_fn_t fn)
+{
+       int indpos = 0;
+       unsigned len = object_list_length(trees);
+       struct tree_entry_list **posns;
+       int i;
+       struct object_list *posn = trees;
+       merge_size = len;
+
+       if (len) {
+               posns = xmalloc(len * sizeof(struct tree_entry_list *));
+               for (i = 0; i < len; i++) {
+                       posns[i] = ((struct tree *) posn->item)->entries;
+                       posn = posn->next;
+               }
+               if (unpack_trees_rec(posns, len, "", fn, &indpos))
+                       return -1;
+       }
+
+       if (trivial_merges_only && nontrivial_merge)
+               die("Merge requires file-level merging");
+
+       check_updates(active_cache, active_nr);
+       return 0;
+}
+
+static int list_tree(unsigned char *sha1)
+{
+       struct tree *tree = parse_tree_indirect(sha1);
+       if (!tree)
+               return -1;
+       object_list_append(&tree->object, &trees);
+       return 0;
+}
+
+static int same(struct cache_entry *a, struct cache_entry *b)
+{
+       if (!!a != !!b)
+               return 0;
+       if (!a && !b)
+               return 1;
+       return a->ce_mode == b->ce_mode && 
+               !memcmp(a->sha1, b->sha1, 20);
+}
+
+
+/*
+ * When a CE gets turned into an unmerged entry, we
+ * want it to be up-to-date
+ */
+static void verify_uptodate(struct cache_entry *ce)
+{
+       struct stat st;
+
+       if (index_only || reset)
+               return;
+
+       if (!lstat(ce->name, &st)) {
+               unsigned changed = ce_match_stat(ce, &st, 1);
+               if (!changed)
+                       return;
+               errno = 0;
+       }
+       if (reset) {
+               ce->ce_flags |= htons(CE_UPDATE);
+               return;
+       }
+       if (errno == ENOENT)
+               return;
+       die("Entry '%s' not uptodate. Cannot merge.", ce->name);
+}
+
+/*
+ * We do not want to remove or overwrite a working tree file that
+ * is not tracked.
+ */
+static void verify_absent(const char *path, const char *action)
+{
+       struct stat st;
+
+       if (index_only || reset || !update)
+               return;
+       if (!lstat(path, &st))
+               die("Untracked working tree file '%s' "
+                   "would be %s by merge.", path, action);
+}
+
+static int merged_entry(struct cache_entry *merge, struct cache_entry *old)
+{
+       merge->ce_flags |= htons(CE_UPDATE);
+       if (old) {
+               /*
+                * See if we can re-use the old CE directly?
+                * That way we get the uptodate stat info.
+                *
+                * This also removes the UPDATE flag on
+                * a match.
+                */
+               if (same(old, merge)) {
+                       *merge = *old;
+               } else {
+                       verify_uptodate(old);
+               }
+       }
+       else
+               verify_absent(merge->name, "overwritten");
+
+       merge->ce_flags &= ~htons(CE_STAGEMASK);
+       add_cache_entry(merge, ADD_CACHE_OK_TO_ADD);
+       return 1;
+}
+
+static int deleted_entry(struct cache_entry *ce, struct cache_entry *old)
+{
+       if (old)
+               verify_uptodate(old);
+       else
+               verify_absent(ce->name, "removed");
+       ce->ce_mode = 0;
+       add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
+       return 1;
+}
+
+static int keep_entry(struct cache_entry *ce)
+{
+       add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
+       return 1;
+}
+
+#if DBRT_DEBUG
+static void show_stage_entry(FILE *o,
+                            const char *label, const struct cache_entry *ce)
+{
+       if (!ce)
+               fprintf(o, "%s (missing)\n", label);
+       else
+               fprintf(o, "%s%06o %s %d\t%s\n",
+                       label,
+                       ntohl(ce->ce_mode),
+                       sha1_to_hex(ce->sha1),
+                       ce_stage(ce),
+                       ce->name);
+}
+#endif
+
+static int threeway_merge(struct cache_entry **stages)
+{
+       struct cache_entry *index;
+       struct cache_entry *head; 
+       struct cache_entry *remote = stages[head_idx + 1];
+       int count;
+       int head_match = 0;
+       int remote_match = 0;
+       const char *path = NULL;
+
+       int df_conflict_head = 0;
+       int df_conflict_remote = 0;
+
+       int any_anc_missing = 0;
+       int no_anc_exists = 1;
+       int i;
+
+       for (i = 1; i < head_idx; i++) {
+               if (!stages[i])
+                       any_anc_missing = 1;
+               else {
+                       if (!path)
+                               path = stages[i]->name;
+                       no_anc_exists = 0;
+               }
+       }
+
+       index = stages[0];
+       head = stages[head_idx];
+
+       if (head == &df_conflict_entry) {
+               df_conflict_head = 1;
+               head = NULL;
+       }
+
+       if (remote == &df_conflict_entry) {
+               df_conflict_remote = 1;
+               remote = NULL;
+       }
+
+       if (!path && index)
+               path = index->name;
+       if (!path && head)
+               path = head->name;
+       if (!path && remote)
+               path = remote->name;
+
+       /* First, if there's a #16 situation, note that to prevent #13
+        * and #14.
+        */
+       if (!same(remote, head)) {
+               for (i = 1; i < head_idx; i++) {
+                       if (same(stages[i], head)) {
+                               head_match = i;
+                       }
+                       if (same(stages[i], remote)) {
+                               remote_match = i;
+                       }
+               }
+       }
+
+       /* We start with cases where the index is allowed to match
+        * something other than the head: #14(ALT) and #2ALT, where it
+        * is permitted to match the result instead.
+        */
+       /* #14, #14ALT, #2ALT */
+       if (remote && !df_conflict_head && head_match && !remote_match) {
+               if (index && !same(index, remote) && !same(index, head))
+                       reject_merge(index);
+               return merged_entry(remote, index);
+       }
+       /*
+        * If we have an entry in the index cache, then we want to
+        * make sure that it matches head.
+        */
+       if (index && !same(index, head)) {
+               reject_merge(index);
+       }
+
+       if (head) {
+               /* #5ALT, #15 */
+               if (same(head, remote))
+                       return merged_entry(head, index);
+               /* #13, #3ALT */
+               if (!df_conflict_remote && remote_match && !head_match)
+                       return merged_entry(head, index);
+       }
+
+       /* #1 */
+       if (!head && !remote && any_anc_missing)
+               return 0;
+
+       /* Under the new "aggressive" rule, we resolve mostly trivial
+        * cases that we historically had git-merge-one-file resolve.
+        */
+       if (aggressive) {
+               int head_deleted = !head && !df_conflict_head;
+               int remote_deleted = !remote && !df_conflict_remote;
+               /*
+                * Deleted in both.
+                * Deleted in one and unchanged in the other.
+                */
+               if ((head_deleted && remote_deleted) ||
+                   (head_deleted && remote && remote_match) ||
+                   (remote_deleted && head && head_match)) {
+                       if (index)
+                               return deleted_entry(index, index);
+                       else if (path)
+                               verify_absent(path, "removed");
+                       return 0;
+               }
+               /*
+                * Added in both, identically.
+                */
+               if (no_anc_exists && head && remote && same(head, remote))
+                       return merged_entry(head, index);
+
+       }
+
+       /* Below are "no merge" cases, which require that the index be
+        * up-to-date to avoid the files getting overwritten with
+        * conflict resolution files. 
+        */
+       if (index) {
+               verify_uptodate(index);
+       }
+       else if (path)
+               verify_absent(path, "overwritten");
+
+       nontrivial_merge = 1;
+
+       /* #2, #3, #4, #6, #7, #9, #11. */
+       count = 0;
+       if (!head_match || !remote_match) {
+               for (i = 1; i < head_idx; i++) {
+                       if (stages[i]) {
+                               keep_entry(stages[i]);
+                               count++;
+                               break;
+                       }
+               }
+       }
+#if DBRT_DEBUG
+       else {
+               fprintf(stderr, "read-tree: warning #16 detected\n");
+               show_stage_entry(stderr, "head   ", stages[head_match]);
+               show_stage_entry(stderr, "remote ", stages[remote_match]);
+       }
+#endif
+       if (head) { count += keep_entry(head); }
+       if (remote) { count += keep_entry(remote); }
+       return count;
+}
+
+/*
+ * Two-way merge.
+ *
+ * The rule is to "carry forward" what is in the index without losing
+ * information across a "fast forward", favoring a successful merge
+ * over a merge failure when it makes sense.  For details of the
+ * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
+ *
+ */
+static int twoway_merge(struct cache_entry **src)
+{
+       struct cache_entry *current = src[0];
+       struct cache_entry *oldtree = src[1], *newtree = src[2];
+
+       if (merge_size != 2)
+               return error("Cannot do a twoway merge of %d trees",
+                            merge_size);
+
+       if (current) {
+               if ((!oldtree && !newtree) || /* 4 and 5 */
+                   (!oldtree && newtree &&
+                    same(current, newtree)) || /* 6 and 7 */
+                   (oldtree && newtree &&
+                    same(oldtree, newtree)) || /* 14 and 15 */
+                   (oldtree && newtree &&
+                    !same(oldtree, newtree) && /* 18 and 19*/
+                    same(current, newtree))) {
+                       return keep_entry(current);
+               }
+               else if (oldtree && !newtree && same(current, oldtree)) {
+                       /* 10 or 11 */
+                       return deleted_entry(oldtree, current);
+               }
+               else if (oldtree && newtree &&
+                        same(current, oldtree) && !same(current, newtree)) {
+                       /* 20 or 21 */
+                       return merged_entry(newtree, current);
+               }
+               else {
+                       /* all other failures */
+                       if (oldtree)
+                               reject_merge(oldtree);
+                       if (current)
+                               reject_merge(current);
+                       if (newtree)
+                               reject_merge(newtree);
+                       return -1;
+               }
+       }
+       else if (newtree)
+               return merged_entry(newtree, current);
+       else
+               return deleted_entry(oldtree, current);
+}
+
+/*
+ * One-way merge.
+ *
+ * The rule is:
+ * - take the stat information from stage0, take the data from stage1
+ */
+static int oneway_merge(struct cache_entry **src)
+{
+       struct cache_entry *old = src[0];
+       struct cache_entry *a = src[1];
+
+       if (merge_size != 1)
+               return error("Cannot do a oneway merge of %d trees",
+                            merge_size);
+
+       if (!a)
+               return deleted_entry(old, old);
+       if (old && same(old, a)) {
+               if (reset) {
+                       struct stat st;
+                       if (lstat(old->name, &st) ||
+                           ce_match_stat(old, &st, 1))
+                               old->ce_flags |= htons(CE_UPDATE);
+               }
+               return keep_entry(old);
+       }
+       return merged_entry(a, old);
+}
+
+static int read_cache_unmerged(void)
+{
+       int i, deleted;
+       struct cache_entry **dst;
+
+       read_cache();
+       dst = active_cache;
+       deleted = 0;
+       for (i = 0; i < active_nr; i++) {
+               struct cache_entry *ce = active_cache[i];
+               if (ce_stage(ce)) {
+                       deleted++;
+                       continue;
+               }
+               if (deleted)
+                       *dst = ce;
+               dst++;
+       }
+       active_nr -= deleted;
+       return deleted;
+}
+
+static const char read_tree_usage[] = "git-read-tree (<sha> | -m [--aggressive] [-u | -i] <sha1> [<sha2> [<sha3>]])";
+
+static struct cache_file cache_file;
+
+int cmd_read_tree(int argc, const char **argv, char **envp)
+{
+       int i, newfd, stage = 0;
+       unsigned char sha1[20];
+       merge_fn_t fn = NULL;
+
+       setup_git_directory();
+       git_config(git_default_config);
+
+       newfd = hold_index_file_for_update(&cache_file, get_index_file());
+       if (newfd < 0)
+               die("unable to create new cachefile");
+
+       git_config(git_default_config);
+
+       merge = 0;
+       reset = 0;
+       for (i = 1; i < argc; i++) {
+               const char *arg = argv[i];
+
+               /* "-u" means "update", meaning that a merge will update
+                * the working tree.
+                */
+               if (!strcmp(arg, "-u")) {
+                       update = 1;
+                       continue;
+               }
+
+               if (!strcmp(arg, "-v")) {
+                       verbose_update = 1;
+                       continue;
+               }
+
+               /* "-i" means "index only", meaning that a merge will
+                * not even look at the working tree.
+                */
+               if (!strcmp(arg, "-i")) {
+                       index_only = 1;
+                       continue;
+               }
+
+               /* This differs from "-m" in that we'll silently ignore unmerged entries */
+               if (!strcmp(arg, "--reset")) {
+                       if (stage || merge)
+                               usage(read_tree_usage);
+                       reset = 1;
+                       merge = 1;
+                       stage = 1;
+                       read_cache_unmerged();
+                       continue;
+               }
+
+               if (!strcmp(arg, "--trivial")) {
+                       trivial_merges_only = 1;
+                       continue;
+               }
+
+               if (!strcmp(arg, "--aggressive")) {
+                       aggressive = 1;
+                       continue;
+               }
+
+               /* "-m" stands for "merge", meaning we start in stage 1 */
+               if (!strcmp(arg, "-m")) {
+                       if (stage || merge)
+                               usage(read_tree_usage);
+                       if (read_cache_unmerged())
+                               die("you need to resolve your current index first");
+                       stage = 1;
+                       merge = 1;
+                       continue;
+               }
+
+               /* using -u and -i at the same time makes no sense */
+               if (1 < index_only + update)
+                       usage(read_tree_usage);
+
+               if (get_sha1(arg, sha1))
+                       die("Not a valid object name %s", arg);
+               if (list_tree(sha1) < 0)
+                       die("failed to unpack tree object %s", arg);
+               stage++;
+       }
+       if ((update||index_only) && !merge)
+               usage(read_tree_usage);
+
+       if (merge) {
+               if (stage < 2)
+                       die("just how do you expect me to merge %d trees?", stage-1);
+               switch (stage - 1) {
+               case 1:
+                       fn = oneway_merge;
+                       break;
+               case 2:
+                       fn = twoway_merge;
+                       break;
+               case 3:
+                       fn = threeway_merge;
+                       break;
+               default:
+                       fn = threeway_merge;
+                       break;
+               }
+
+               if (stage - 1 >= 3)
+                       head_idx = stage - 2;
+               else
+                       head_idx = 1;
+       }
+
+       unpack_trees(fn);
+       if (write_cache(newfd, active_cache, active_nr) ||
+           commit_index_file(&cache_file))
+               die("unable to write new index file");
+       return 0;
+}

diff --git a/builtin.h b/builtin.h
index d2105439482d51c166352e48c08bca21ee1a5490..88b3523c25a30c15b93f51ec84265a0441994547 100644 (file)
--- a/builtin.h
+++ b/builtin.h
@@ -30,5 +30,6 @@ extern int cmd_init_db(int argc, const char **argv, char **envp);
 extern int cmd_ls_files(int argc, const char **argv, char **envp);
 extern int cmd_ls_tree(int argc, const char **argv, char **envp);
 extern int cmd_tar_tree(int argc, const char **argv, char **envp);
+extern int cmd_read_tree(int argc, const char **argv, char **envp);
 
 #endif

diff --git a/git.c b/git.c
index c253e609532cbf115bf06ed53aec0d138650f001..300e2b269cb7fa823e211e76605c04b5aaa8375d 100644 (file)
--- a/git.c
+++ b/git.c
@@ -55,7 +55,8 @@ static void handle_internal_command(int argc, const char **argv, char **envp)
                { "check-ref-format", cmd_check_ref_format },
                { "ls-files", cmd_ls_files },
                { "ls-tree", cmd_ls_tree },
-               { "tar-tree", cmd_tar_tree }
+               { "tar-tree", cmd_tar_tree },
+               { "read-tree", cmd_read_tree }
        };
        int i;
 

diff --git a/read-tree.c b/read-tree.c
deleted file mode 100644 (file)
index 82e2a9a..0000000
--- a/read-tree.c
+++ /dev/null
@@ -1,881 +0,0 @@
-/*
- * GIT - The information manager from hell
- *
- * Copyright (C) Linus Torvalds, 2005
- */
-#define DBRT_DEBUG 1
-
-#include "cache.h"
-
-#include "object.h"
-#include "tree.h"
-#include <sys/time.h>
-#include <signal.h>
-
-static int reset = 0;
-static int merge = 0;
-static int update = 0;
-static int index_only = 0;
-static int nontrivial_merge = 0;
-static int trivial_merges_only = 0;
-static int aggressive = 0;
-static int verbose_update = 0;
-static volatile int progress_update = 0;
-
-static int head_idx = -1;
-static int merge_size = 0;
-
-static struct object_list *trees = NULL;
-
-static struct cache_entry df_conflict_entry = { 
-};
-
-static struct tree_entry_list df_conflict_list = {
-       .name = NULL,
-       .next = &df_conflict_list
-};
-
-typedef int (*merge_fn_t)(struct cache_entry **src);
-
-static int entcmp(char *name1, int dir1, char *name2, int dir2)
-{
-       int len1 = strlen(name1);
-       int len2 = strlen(name2);
-       int len = len1 < len2 ? len1 : len2;
-       int ret = memcmp(name1, name2, len);
-       unsigned char c1, c2;
-       if (ret)
-               return ret;
-       c1 = name1[len];
-       c2 = name2[len];
-       if (!c1 && dir1)
-               c1 = '/';
-       if (!c2 && dir2)
-               c2 = '/';
-       ret = (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
-       if (c1 && c2 && !ret)
-               ret = len1 - len2;
-       return ret;
-}
-
-static int unpack_trees_rec(struct tree_entry_list **posns, int len,
-                           const char *base, merge_fn_t fn, int *indpos)
-{
-       int baselen = strlen(base);
-       int src_size = len + 1;
-       do {
-               int i;
-               char *first;
-               int firstdir = 0;
-               int pathlen;
-               unsigned ce_size;
-               struct tree_entry_list **subposns;
-               struct cache_entry **src;
-               int any_files = 0;
-               int any_dirs = 0;
-               char *cache_name;
-               int ce_stage;
-
-               /* Find the first name in the input. */
-
-               first = NULL;
-               cache_name = NULL;
-
-               /* Check the cache */
-               if (merge && *indpos < active_nr) {
-                       /* This is a bit tricky: */
-                       /* If the index has a subdirectory (with
-                        * contents) as the first name, it'll get a
-                        * filename like "foo/bar". But that's after
-                        * "foo", so the entry in trees will get
-                        * handled first, at which point we'll go into
-                        * "foo", and deal with "bar" from the index,
-                        * because the base will be "foo/". The only
-                        * way we can actually have "foo/bar" first of
-                        * all the things is if the trees don't
-                        * contain "foo" at all, in which case we'll
-                        * handle "foo/bar" without going into the
-                        * directory, but that's fine (and will return
-                        * an error anyway, with the added unknown
-                        * file case.
-                        */
-
-                       cache_name = active_cache[*indpos]->name;
-                       if (strlen(cache_name) > baselen &&
-                           !memcmp(cache_name, base, baselen)) {
-                               cache_name += baselen;
-                               first = cache_name;
-                       } else {
-                               cache_name = NULL;
-                       }
-               }
-
-#if DBRT_DEBUG > 1
-               if (first)
-                       printf("index %s\n", first);
-#endif
-               for (i = 0; i < len; i++) {
-                       if (!posns[i] || posns[i] == &df_conflict_list)
-                               continue;
-#if DBRT_DEBUG > 1
-                       printf("%d %s\n", i + 1, posns[i]->name);
-#endif
-                       if (!first || entcmp(first, firstdir,
-                                            posns[i]->name, 
-                                            posns[i]->directory) > 0) {
-                               first = posns[i]->name;
-                               firstdir = posns[i]->directory;
-                       }
-               }
-               /* No name means we're done */
-               if (!first)
-                       return 0;
-
-               pathlen = strlen(first);
-               ce_size = cache_entry_size(baselen + pathlen);
-
-               src = xcalloc(src_size, sizeof(struct cache_entry *));
-
-               subposns = xcalloc(len, sizeof(struct tree_list_entry *));
-
-               if (cache_name && !strcmp(cache_name, first)) {
-                       any_files = 1;
-                       src[0] = active_cache[*indpos];
-                       remove_cache_entry_at(*indpos);
-               }
-
-               for (i = 0; i < len; i++) {
-                       struct cache_entry *ce;
-
-                       if (!posns[i] ||
-                           (posns[i] != &df_conflict_list &&
-                            strcmp(first, posns[i]->name))) {
-                               continue;
-                       }
-
-                       if (posns[i] == &df_conflict_list) {
-                               src[i + merge] = &df_conflict_entry;
-                               continue;
-                       }
-
-                       if (posns[i]->directory) {
-                               any_dirs = 1;
-                               parse_tree(posns[i]->item.tree);
-                               subposns[i] = posns[i]->item.tree->entries;
-                               posns[i] = posns[i]->next;
-                               src[i + merge] = &df_conflict_entry;
-                               continue;
-                       }
-
-                       if (!merge)
-                               ce_stage = 0;
-                       else if (i + 1 < head_idx)
-                               ce_stage = 1;
-                       else if (i + 1 > head_idx)
-                               ce_stage = 3;
-                       else
-                               ce_stage = 2;
-
-                       ce = xcalloc(1, ce_size);
-                       ce->ce_mode = create_ce_mode(posns[i]->mode);
-                       ce->ce_flags = create_ce_flags(baselen + pathlen,
-                                                      ce_stage);
-                       memcpy(ce->name, base, baselen);
-                       memcpy(ce->name + baselen, first, pathlen + 1);
-
-                       any_files = 1;
-
-                       memcpy(ce->sha1, posns[i]->item.any->sha1, 20);
-                       src[i + merge] = ce;
-                       subposns[i] = &df_conflict_list;
-                       posns[i] = posns[i]->next;
-               }
-               if (any_files) {
-                       if (merge) {
-                               int ret;
-
-#if DBRT_DEBUG > 1
-                               printf("%s:\n", first);
-                               for (i = 0; i < src_size; i++) {
-                                       printf(" %d ", i);
-                                       if (src[i])
-                                               printf("%s\n", sha1_to_hex(src[i]->sha1));
-                                       else
-                                               printf("\n");
-                               }
-#endif
-                               ret = fn(src);
-                               
-#if DBRT_DEBUG > 1
-                               printf("Added %d entries\n", ret);
-#endif
-                               *indpos += ret;
-                       } else {
-                               for (i = 0; i < src_size; i++) {
-                                       if (src[i]) {
-                                               add_cache_entry(src[i], ADD_CACHE_OK_TO_ADD|ADD_CACHE_SKIP_DFCHECK);
-                                       }
-                               }
-                       }
-               }
-               if (any_dirs) {
-                       char *newbase = xmalloc(baselen + 2 + pathlen);
-                       memcpy(newbase, base, baselen);
-                       memcpy(newbase + baselen, first, pathlen);
-                       newbase[baselen + pathlen] = '/';
-                       newbase[baselen + pathlen + 1] = '\0';
-                       if (unpack_trees_rec(subposns, len, newbase, fn,
-                                            indpos))
-                               return -1;
-                       free(newbase);
-               }
-               free(subposns);
-               free(src);
-       } while (1);
-}
-
-static void reject_merge(struct cache_entry *ce)
-{
-       die("Entry '%s' would be overwritten by merge. Cannot merge.", 
-           ce->name);
-}
-
-/* Unlink the last component and attempt to remove leading
- * directories, in case this unlink is the removal of the
- * last entry in the directory -- empty directories are removed.
- */
-static void unlink_entry(char *name)
-{
-       char *cp, *prev;
-
-       if (unlink(name))
-               return;
-       prev = NULL;
-       while (1) {
-               int status;
-               cp = strrchr(name, '/');
-               if (prev)
-                       *prev = '/';
-               if (!cp)
-                       break;
-
-               *cp = 0;
-               status = rmdir(name);
-               if (status) {
-                       *cp = '/';
-                       break;
-               }
-               prev = cp;
-       }
-}
-
-static void progress_interval(int signum)
-{
-       progress_update = 1;
-}
-
-static void setup_progress_signal(void)
-{
-       struct sigaction sa;
-       struct itimerval v;
-
-       memset(&sa, 0, sizeof(sa));
-       sa.sa_handler = progress_interval;
-       sigemptyset(&sa.sa_mask);
-       sa.sa_flags = SA_RESTART;
-       sigaction(SIGALRM, &sa, NULL);
-
-       v.it_interval.tv_sec = 1;
-       v.it_interval.tv_usec = 0;
-       v.it_value = v.it_interval;
-       setitimer(ITIMER_REAL, &v, NULL);
-}
-
-static void check_updates(struct cache_entry **src, int nr)
-{
-       static struct checkout state = {
-               .base_dir = "",
-               .force = 1,
-               .quiet = 1,
-               .refresh_cache = 1,
-       };
-       unsigned short mask = htons(CE_UPDATE);
-       unsigned last_percent = 200, cnt = 0, total = 0;
-
-       if (update && verbose_update) {
-               for (total = cnt = 0; cnt < nr; cnt++) {
-                       struct cache_entry *ce = src[cnt];
-                       if (!ce->ce_mode || ce->ce_flags & mask)
-                               total++;
-               }
-
-               /* Don't bother doing this for very small updates */
-               if (total < 250)
-                       total = 0;
-
-               if (total) {
-                       fprintf(stderr, "Checking files out...\n");
-                       setup_progress_signal();
-                       progress_update = 1;
-               }
-               cnt = 0;
-       }
-
-       while (nr--) {
-               struct cache_entry *ce = *src++;
-
-               if (total) {
-                       if (!ce->ce_mode || ce->ce_flags & mask) {
-                               unsigned percent;
-                               cnt++;
-                               percent = (cnt * 100) / total;
-                               if (percent != last_percent ||
-                                   progress_update) {
-                                       fprintf(stderr, "%4u%% (%u/%u) done\r",
-                                               percent, cnt, total);
-                                       last_percent = percent;
-                               }
-                       }
-               }
-               if (!ce->ce_mode) {
-                       if (update)
-                               unlink_entry(ce->name);
-                       continue;
-               }
-               if (ce->ce_flags & mask) {
-                       ce->ce_flags &= ~mask;
-                       if (update)
-                               checkout_entry(ce, &state, NULL);
-               }
-       }
-       if (total) {
-               signal(SIGALRM, SIG_IGN);
-               fputc('\n', stderr);
-       }
-}
-
-static int unpack_trees(merge_fn_t fn)
-{
-       int indpos = 0;
-       unsigned len = object_list_length(trees);
-       struct tree_entry_list **posns;
-       int i;
-       struct object_list *posn = trees;
-       merge_size = len;
-
-       if (len) {
-               posns = xmalloc(len * sizeof(struct tree_entry_list *));
-               for (i = 0; i < len; i++) {
-                       posns[i] = ((struct tree *) posn->item)->entries;
-                       posn = posn->next;
-               }
-               if (unpack_trees_rec(posns, len, "", fn, &indpos))
-                       return -1;
-       }
-
-       if (trivial_merges_only && nontrivial_merge)
-               die("Merge requires file-level merging");
-
-       check_updates(active_cache, active_nr);
-       return 0;
-}
-
-static int list_tree(unsigned char *sha1)
-{
-       struct tree *tree = parse_tree_indirect(sha1);
-       if (!tree)
-               return -1;
-       object_list_append(&tree->object, &trees);
-       return 0;
-}
-
-static int same(struct cache_entry *a, struct cache_entry *b)
-{
-       if (!!a != !!b)
-               return 0;
-       if (!a && !b)
-               return 1;
-       return a->ce_mode == b->ce_mode && 
-               !memcmp(a->sha1, b->sha1, 20);
-}
-
-
-/*
- * When a CE gets turned into an unmerged entry, we
- * want it to be up-to-date
- */
-static void verify_uptodate(struct cache_entry *ce)
-{
-       struct stat st;
-
-       if (index_only || reset)
-               return;
-
-       if (!lstat(ce->name, &st)) {
-               unsigned changed = ce_match_stat(ce, &st, 1);
-               if (!changed)
-                       return;
-               errno = 0;
-       }
-       if (reset) {
-               ce->ce_flags |= htons(CE_UPDATE);
-               return;
-       }
-       if (errno == ENOENT)
-               return;
-       die("Entry '%s' not uptodate. Cannot merge.", ce->name);
-}
-
-/*
- * We do not want to remove or overwrite a working tree file that
- * is not tracked.
- */
-static void verify_absent(const char *path, const char *action)
-{
-       struct stat st;
-
-       if (index_only || reset || !update)
-               return;
-       if (!lstat(path, &st))
-               die("Untracked working tree file '%s' "
-                   "would be %s by merge.", path, action);
-}
-
-static int merged_entry(struct cache_entry *merge, struct cache_entry *old)
-{
-       merge->ce_flags |= htons(CE_UPDATE);
-       if (old) {
-               /*
-                * See if we can re-use the old CE directly?
-                * That way we get the uptodate stat info.
-                *
-                * This also removes the UPDATE flag on
-                * a match.
-                */
-               if (same(old, merge)) {
-                       *merge = *old;
-               } else {
-                       verify_uptodate(old);
-               }
-       }
-       else
-               verify_absent(merge->name, "overwritten");
-
-       merge->ce_flags &= ~htons(CE_STAGEMASK);
-       add_cache_entry(merge, ADD_CACHE_OK_TO_ADD);
-       return 1;
-}
-
-static int deleted_entry(struct cache_entry *ce, struct cache_entry *old)
-{
-       if (old)
-               verify_uptodate(old);
-       else
-               verify_absent(ce->name, "removed");
-       ce->ce_mode = 0;
-       add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
-       return 1;
-}
-
-static int keep_entry(struct cache_entry *ce)
-{
-       add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
-       return 1;
-}
-
-#if DBRT_DEBUG
-static void show_stage_entry(FILE *o,
-                            const char *label, const struct cache_entry *ce)
-{
-       if (!ce)
-               fprintf(o, "%s (missing)\n", label);
-       else
-               fprintf(o, "%s%06o %s %d\t%s\n",
-                       label,
-                       ntohl(ce->ce_mode),
-                       sha1_to_hex(ce->sha1),
-                       ce_stage(ce),
-                       ce->name);
-}
-#endif
-
-static int threeway_merge(struct cache_entry **stages)
-{
-       struct cache_entry *index;
-       struct cache_entry *head; 
-       struct cache_entry *remote = stages[head_idx + 1];
-       int count;
-       int head_match = 0;
-       int remote_match = 0;
-       const char *path = NULL;
-
-       int df_conflict_head = 0;
-       int df_conflict_remote = 0;
-
-       int any_anc_missing = 0;
-       int no_anc_exists = 1;
-       int i;
-
-       for (i = 1; i < head_idx; i++) {
-               if (!stages[i])
-                       any_anc_missing = 1;
-               else {
-                       if (!path)
-                               path = stages[i]->name;
-                       no_anc_exists = 0;
-               }
-       }
-
-       index = stages[0];
-       head = stages[head_idx];
-
-       if (head == &df_conflict_entry) {
-               df_conflict_head = 1;
-               head = NULL;
-       }
-
-       if (remote == &df_conflict_entry) {
-               df_conflict_remote = 1;
-               remote = NULL;
-       }
-
-       if (!path && index)
-               path = index->name;
-       if (!path && head)
-               path = head->name;
-       if (!path && remote)
-               path = remote->name;
-
-       /* First, if there's a #16 situation, note that to prevent #13
-        * and #14.
-        */
-       if (!same(remote, head)) {
-               for (i = 1; i < head_idx; i++) {
-                       if (same(stages[i], head)) {
-                               head_match = i;
-                       }
-                       if (same(stages[i], remote)) {
-                               remote_match = i;
-                       }
-               }
-       }
-
-       /* We start with cases where the index is allowed to match
-        * something other than the head: #14(ALT) and #2ALT, where it
-        * is permitted to match the result instead.
-        */
-       /* #14, #14ALT, #2ALT */
-       if (remote && !df_conflict_head && head_match && !remote_match) {
-               if (index && !same(index, remote) && !same(index, head))
-                       reject_merge(index);
-               return merged_entry(remote, index);
-       }
-       /*
-        * If we have an entry in the index cache, then we want to
-        * make sure that it matches head.
-        */
-       if (index && !same(index, head)) {
-               reject_merge(index);
-       }
-
-       if (head) {
-               /* #5ALT, #15 */
-               if (same(head, remote))
-                       return merged_entry(head, index);
-               /* #13, #3ALT */
-               if (!df_conflict_remote && remote_match && !head_match)
-                       return merged_entry(head, index);
-       }
-
-       /* #1 */
-       if (!head && !remote && any_anc_missing)
-               return 0;
-
-       /* Under the new "aggressive" rule, we resolve mostly trivial
-        * cases that we historically had git-merge-one-file resolve.
-        */
-       if (aggressive) {
-               int head_deleted = !head && !df_conflict_head;
-               int remote_deleted = !remote && !df_conflict_remote;
-               /*
-                * Deleted in both.
-                * Deleted in one and unchanged in the other.
-                */
-               if ((head_deleted && remote_deleted) ||
-                   (head_deleted && remote && remote_match) ||
-                   (remote_deleted && head && head_match)) {
-                       if (index)
-                               return deleted_entry(index, index);
-                       else if (path)
-                               verify_absent(path, "removed");
-                       return 0;
-               }
-               /*
-                * Added in both, identically.
-                */
-               if (no_anc_exists && head && remote && same(head, remote))
-                       return merged_entry(head, index);
-
-       }
-
-       /* Below are "no merge" cases, which require that the index be
-        * up-to-date to avoid the files getting overwritten with
-        * conflict resolution files. 
-        */
-       if (index) {
-               verify_uptodate(index);
-       }
-       else if (path)
-               verify_absent(path, "overwritten");
-
-       nontrivial_merge = 1;
-
-       /* #2, #3, #4, #6, #7, #9, #11. */
-       count = 0;
-       if (!head_match || !remote_match) {
-               for (i = 1; i < head_idx; i++) {
-                       if (stages[i]) {
-                               keep_entry(stages[i]);
-                               count++;
-                               break;
-                       }
-               }
-       }
-#if DBRT_DEBUG
-       else {
-               fprintf(stderr, "read-tree: warning #16 detected\n");
-               show_stage_entry(stderr, "head   ", stages[head_match]);
-               show_stage_entry(stderr, "remote ", stages[remote_match]);
-       }
-#endif
-       if (head) { count += keep_entry(head); }
-       if (remote) { count += keep_entry(remote); }
-       return count;
-}
-
-/*
- * Two-way merge.
- *
- * The rule is to "carry forward" what is in the index without losing
- * information across a "fast forward", favoring a successful merge
- * over a merge failure when it makes sense.  For details of the
- * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
- *
- */
-static int twoway_merge(struct cache_entry **src)
-{
-       struct cache_entry *current = src[0];
-       struct cache_entry *oldtree = src[1], *newtree = src[2];
-
-       if (merge_size != 2)
-               return error("Cannot do a twoway merge of %d trees",
-                            merge_size);
-
-       if (current) {
-               if ((!oldtree && !newtree) || /* 4 and 5 */
-                   (!oldtree && newtree &&
-                    same(current, newtree)) || /* 6 and 7 */
-                   (oldtree && newtree &&
-                    same(oldtree, newtree)) || /* 14 and 15 */
-                   (oldtree && newtree &&
-                    !same(oldtree, newtree) && /* 18 and 19*/
-                    same(current, newtree))) {
-                       return keep_entry(current);
-               }
-               else if (oldtree && !newtree && same(current, oldtree)) {
-                       /* 10 or 11 */
-                       return deleted_entry(oldtree, current);
-               }
-               else if (oldtree && newtree &&
-                        same(current, oldtree) && !same(current, newtree)) {
-                       /* 20 or 21 */
-                       return merged_entry(newtree, current);
-               }
-               else {
-                       /* all other failures */
-                       if (oldtree)
-                               reject_merge(oldtree);
-                       if (current)
-                               reject_merge(current);
-                       if (newtree)
-                               reject_merge(newtree);
-                       return -1;
-               }
-       }
-       else if (newtree)
-               return merged_entry(newtree, current);
-       else
-               return deleted_entry(oldtree, current);
-}
-
-/*
- * One-way merge.
- *
- * The rule is:
- * - take the stat information from stage0, take the data from stage1
- */
-static int oneway_merge(struct cache_entry **src)
-{
-       struct cache_entry *old = src[0];
-       struct cache_entry *a = src[1];
-
-       if (merge_size != 1)
-               return error("Cannot do a oneway merge of %d trees",
-                            merge_size);
-
-       if (!a)
-               return deleted_entry(old, old);
-       if (old && same(old, a)) {
-               if (reset) {
-                       struct stat st;
-                       if (lstat(old->name, &st) ||
-                           ce_match_stat(old, &st, 1))
-                               old->ce_flags |= htons(CE_UPDATE);
-               }
-               return keep_entry(old);
-       }
-       return merged_entry(a, old);
-}
-
-static int read_cache_unmerged(void)
-{
-       int i, deleted;
-       struct cache_entry **dst;
-
-       read_cache();
-       dst = active_cache;
-       deleted = 0;
-       for (i = 0; i < active_nr; i++) {
-               struct cache_entry *ce = active_cache[i];
-               if (ce_stage(ce)) {
-                       deleted++;
-                       continue;
-               }
-               if (deleted)
-                       *dst = ce;
-               dst++;
-       }
-       active_nr -= deleted;
-       return deleted;
-}
-
-static const char read_tree_usage[] = "git-read-tree (<sha> | -m [--aggressive] [-u | -i] <sha1> [<sha2> [<sha3>]])";
-
-static struct cache_file cache_file;
-
-int main(int argc, char **argv)
-{
-       int i, newfd, stage = 0;
-       unsigned char sha1[20];
-       merge_fn_t fn = NULL;
-
-       setup_git_directory();
-       git_config(git_default_config);
-
-       newfd = hold_index_file_for_update(&cache_file, get_index_file());
-       if (newfd < 0)
-               die("unable to create new cachefile");
-
-       git_config(git_default_config);
-
-       merge = 0;
-       reset = 0;
-       for (i = 1; i < argc; i++) {
-               const char *arg = argv[i];
-
-               /* "-u" means "update", meaning that a merge will update
-                * the working tree.
-                */
-               if (!strcmp(arg, "-u")) {
-                       update = 1;
-                       continue;
-               }
-
-               if (!strcmp(arg, "-v")) {
-                       verbose_update = 1;
-                       continue;
-               }
-
-               /* "-i" means "index only", meaning that a merge will
-                * not even look at the working tree.
-                */
-               if (!strcmp(arg, "-i")) {
-                       index_only = 1;
-                       continue;
-               }
-
-               /* This differs from "-m" in that we'll silently ignore unmerged entries */
-               if (!strcmp(arg, "--reset")) {
-                       if (stage || merge)
-                               usage(read_tree_usage);
-                       reset = 1;
-                       merge = 1;
-                       stage = 1;
-                       read_cache_unmerged();
-                       continue;
-               }
-
-               if (!strcmp(arg, "--trivial")) {
-                       trivial_merges_only = 1;
-                       continue;
-               }
-
-               if (!strcmp(arg, "--aggressive")) {
-                       aggressive = 1;
-                       continue;
-               }
-
-               /* "-m" stands for "merge", meaning we start in stage 1 */
-               if (!strcmp(arg, "-m")) {
-                       if (stage || merge)
-                               usage(read_tree_usage);
-                       if (read_cache_unmerged())
-                               die("you need to resolve your current index first");
-                       stage = 1;
-                       merge = 1;
-                       continue;
-               }
-
-               /* using -u and -i at the same time makes no sense */
-               if (1 < index_only + update)
-                       usage(read_tree_usage);
-
-               if (get_sha1(arg, sha1))
-                       die("Not a valid object name %s", arg);
-               if (list_tree(sha1) < 0)
-                       die("failed to unpack tree object %s", arg);
-               stage++;
-       }
-       if ((update||index_only) && !merge)
-               usage(read_tree_usage);
-
-       if (merge) {
-               if (stage < 2)
-                       die("just how do you expect me to merge %d trees?", stage-1);
-               switch (stage - 1) {
-               case 1:
-                       fn = oneway_merge;
-                       break;
-               case 2:
-                       fn = twoway_merge;
-                       break;
-               case 3:
-                       fn = threeway_merge;
-                       break;
-               default:
-                       fn = threeway_merge;
-                       break;
-               }
-
-               if (stage - 1 >= 3)
-                       head_idx = stage - 2;
-               else
-                       head_idx = 1;
-       }
-
-       unpack_trees(fn);
-       if (write_cache(newfd, active_cache, active_nr) ||
-           commit_index_file(&cache_file))
-               die("unable to write new index file");
-       return 0;
-}