Re-implement "check_file_directory_conflict()"

This is (imho) more readable, and is also a lot faster.  The expense of
looking up sub-directory beginnings was killing us on things like
"git-diff-cache", even though that one didn't even care at all about the
file vs directory conflicts.

We really only care when somebody tries to add a conflicting name to
stage 0.

We should go through the conflict rules more carefully some day.

diff --git a/read-cache.c b/read-cache.c
index e9618f0914b36a4d1bd60785e53ad484e8748e36..4b8348ca92b7ea9f955d890c417d05a6816f9ee0 100644 (file)
--- a/read-cache.c
+++ b/read-cache.c
@@ -171,107 +171,106 @@ int ce_same_name(struct cache_entry *a, struct cache_entry *b)
        return ce_namelen(b) == len && !memcmp(a->name, b->name, len);
 }
 
-/* We may be in a situation where we already have path/file and path
- * is being added, or we already have path and path/file is being
- * added.  Either one would result in a nonsense tree that has path
- * twice when git-write-tree tries to write it out.  Prevent it.
- * 
- * If ok-to-replace is specified, we remove the conflicting entries
- * from the cache so the caller should recompute the insert position.
- * When this happens, we return non-zero.
+/*
+ * Do we have another file that has the beginning components being a
+ * proper superset of the name we're trying to add?
  */
-static int check_file_directory_conflict(const struct cache_entry *ce,
-                                        int ok_to_replace)
+static int has_file_name(const struct cache_entry *ce, int pos, int ok_to_replace)
 {
-       int pos, replaced = 0;
-       const char *path = ce->name;
-       int namelen = strlen(path);
-       int stage = ce_stage(ce);
-       char *pathbuf = xmalloc(namelen + 1);
-       char *cp;
+       int retval = 0;
+       int len = ce_namelen(ce);
+       const char *name = ce->name;
 
-       memcpy(pathbuf, path, namelen + 1);
+       while (pos < active_nr) {
+               struct cache_entry *p = active_cache[pos++];
 
-       /*
-        * We are inserting path/file.  Do they have path registered at
-        * the same stage?  We need to do this for all the levels of our
-        * subpath.
-        */
-       cp = pathbuf;
-       while (1) {
-               char *ep = strchr(cp, '/');
-               int len;
-               if (!ep)
+               if (len >= ce_namelen(p))
                        break;
-               *ep = 0;    /* first cut it at slash */
-               len = ep - pathbuf;
-               pos = cache_name_pos(pathbuf,
-                                    ntohs(create_ce_flags(len, stage)));
-               if (0 <= pos) {
-                       /* Our leading path component is registered as a file,
-                        * and we are trying to make it a directory.  This is
-                        * bad.
-                        */
-                       if (!ok_to_replace) {
-                               free(pathbuf);
-                               return -1;
-                       }
-                       fprintf(stderr, "removing file '%s' to replace it with a directory to create '%s'.\n", pathbuf, path);
-                       remove_cache_entry_at(pos);
-                       replaced = 1;
-               }
-               *ep = '/';  /* then restore it and go downwards */
-               cp = ep + 1;
+               if (memcmp(name, p->name, len))
+                       break;
+               if (p->name[len] != '/')
+                       continue;
+fprintf(stderr, "conflict: %s %s\n", ce->name, p->name);
+               retval = -1;
+               if (!ok_to_replace)
+                       break;
+               remove_cache_entry_at(--pos);
        }
-       free(pathbuf);
+       return retval;
+}
 
-       /* Do we have an entry in the cache that makes our path a prefix
-        * of it?  That is, are we creating a file where they already expect
-        * a directory there?
-        */
-       pos = cache_name_pos(path,
-                            ntohs(create_ce_flags(namelen, stage)));
+/*
+ * Do we have another file with a pathname that is a proper
+ * subset of the name we're trying to add?
+ */
+static int has_dir_name(const struct cache_entry *ce, int pos, int ok_to_replace)
+{
+       int retval = 0;
+       const char *name = ce->name;
+       const char *slash = name + ce_namelen(ce);
 
-       /* (0 <= pos) cannot happen because add_cache_entry()
-        * should have taken care of that case.
-        */
-       pos = -pos-1;
+       for (;;) {
+               int len;
 
-       /* pos would point at an existing entry that would come immediately
-        * after our path.  It could be the same as our path in higher stage,
-        * or different path but in a lower stage.
-        *
-        * E.g. when we are inserting path at stage 2,
-        *
-        *        1 path
-        * pos->  3 path
-        *        2 path/file1
-        *        3 path/file1
-        *        2 path/file2
-        *        2 patho
-        *
-        * We need to examine pos, ignore it because it is at different
-        * stage, examine next to find the path/file at stage 2, and
-        * complain.  We need to do this until we are not the leading
-        * path of an existing entry anymore.
-        */
+               for (;;) {
+                       if (*--slash == '/')
+                               break;
+                       if (slash <= ce->name)
+                               return retval;
+               }
+               len = slash - name;
 
-       while (pos < active_nr) {
-               struct cache_entry *other = active_cache[pos];
-               if (strncmp(other->name, path, namelen))
-                       break; /* it is not our "subdirectory" anymore */
-               if ((ce_stage(other) == stage) &&
-                   other->name[namelen] == '/') {
-                       if (!ok_to_replace)
-                               return -1;
-                       fprintf(stderr, "removing file '%s' under '%s' to be replaced with a file\n", other->name, path);
+               pos = cache_name_pos(name, len);
+               if (pos >= 0) {
+                       retval = -1;
+                       if (ok_to_replace)
+                               break;
                        remove_cache_entry_at(pos);
-                       replaced = 1;
-                       continue; /* cycle without updating pos */
+                       continue;
+               }
+
+               /*
+                * Trivial optimization: if we find an entry that
+                * already matches the sub-directory, then we know
+                * we're ok, and we can exit
+                */
+               pos = -pos-1;
+               if (pos < active_nr) {
+                       struct cache_entry *p = active_cache[pos];
+                       if (ce_namelen(p) <= len)
+                               continue;
+                       if (p->name[len] != '/')
+                               continue;
+                       if (memcmp(p->name, name, len))
+                               continue;
+                       break;
                }
-               pos++;
        }
-       return replaced;
+       return retval;
+}
+
+/* We may be in a situation where we already have path/file and path
+ * is being added, or we already have path and path/file is being
+ * added.  Either one would result in a nonsense tree that has path
+ * twice when git-write-tree tries to write it out.  Prevent it.
+ * 
+ * If ok-to-replace is specified, we remove the conflicting entries
+ * from the cache so the caller should recompute the insert position.
+ * When this happens, we return non-zero.
+ */
+static int check_file_directory_conflict(const struct cache_entry *ce, int pos, int ok_to_replace)
+{
+       /*
+        * We check if the path is a sub-path of a subsequent pathname
+        * first, since removing those will not change the position
+        * in the array
+        */
+       int retval = has_file_name(ce, pos, ok_to_replace);
+       /*
+        * Then check if the path might have a clashing sub-directory
+        * before it.
+        */
+       return retval + has_dir_name(ce, pos, ok_to_replace);
 }
 
 int add_cache_entry(struct cache_entry *ce, int option)
@@ -304,7 +303,7 @@ int add_cache_entry(struct cache_entry *ce, int option)
        if (!ok_to_add)
                return -1;
 
-       if (check_file_directory_conflict(ce, ok_to_replace)) {
+       if (!ce_stage(ce) && check_file_directory_conflict(ce, pos, ok_to_replace)) {
                if (!ok_to_replace)
                        return -1;
                pos = cache_name_pos(ce->name, ntohs(ce->ce_flags));