git notes merge: Initial implementation handling trivial merges only

[git.git] / notes-merge.c

diff --git a/notes-merge.c b/notes-merge.c
new file mode 100644 (file)
index 0000000..ab98850
--- /dev/null
+++ b/notes-merge.c
@@ -0,0 +1,120 @@
+#include "cache.h"
+#include "commit.h"
+#include "refs.h"
+#include "notes-merge.h"
+
+void init_notes_merge_options(struct notes_merge_options *o)
+{
+       memset(o, 0, sizeof(struct notes_merge_options));
+       o->verbosity = NOTES_MERGE_VERBOSITY_DEFAULT;
+}
+
+#define OUTPUT(o, v, ...) \
+       do { \
+               if ((o)->verbosity >= (v)) { \
+                       printf(__VA_ARGS__); \
+                       puts(""); \
+               } \
+       } while (0)
+
+int notes_merge(struct notes_merge_options *o,
+               unsigned char *result_sha1)
+{
+       unsigned char local_sha1[20], remote_sha1[20];
+       struct commit *local, *remote;
+       struct commit_list *bases = NULL;
+       const unsigned char *base_sha1;
+       int result = 0;
+
+       assert(o->local_ref && o->remote_ref);
+       hashclr(result_sha1);
+
+       trace_printf("notes_merge(o->local_ref = %s, o->remote_ref = %s)\n",
+              o->local_ref, o->remote_ref);
+
+       /* Dereference o->local_ref into local_sha1 */
+       if (!resolve_ref(o->local_ref, local_sha1, 0, NULL))
+               die("Failed to resolve local notes ref '%s'", o->local_ref);
+       else if (!check_ref_format(o->local_ref) && is_null_sha1(local_sha1))
+               local = NULL; /* local_sha1 == null_sha1 indicates unborn ref */
+       else if (!(local = lookup_commit_reference(local_sha1)))
+               die("Could not parse local commit %s (%s)",
+                   sha1_to_hex(local_sha1), o->local_ref);
+       trace_printf("\tlocal commit: %.7s\n", sha1_to_hex(local_sha1));
+
+       /* Dereference o->remote_ref into remote_sha1 */
+       if (get_sha1(o->remote_ref, remote_sha1)) {
+               /*
+                * Failed to get remote_sha1. If o->remote_ref looks like an
+                * unborn ref, perform the merge using an empty notes tree.
+                */
+               if (!check_ref_format(o->remote_ref)) {
+                       hashclr(remote_sha1);
+                       remote = NULL;
+               } else {
+                       die("Failed to resolve remote notes ref '%s'",
+                           o->remote_ref);
+               }
+       } else if (!(remote = lookup_commit_reference(remote_sha1))) {
+               die("Could not parse remote commit %s (%s)",
+                   sha1_to_hex(remote_sha1), o->remote_ref);
+       }
+       trace_printf("\tremote commit: %.7s\n", sha1_to_hex(remote_sha1));
+
+       if (!local && !remote)
+               die("Cannot merge empty notes ref (%s) into empty notes ref "
+                   "(%s)", o->remote_ref, o->local_ref);
+       if (!local) {
+               /* result == remote commit */
+               hashcpy(result_sha1, remote_sha1);
+               goto found_result;
+       }
+       if (!remote) {
+               /* result == local commit */
+               hashcpy(result_sha1, local_sha1);
+               goto found_result;
+       }
+       assert(local && remote);
+
+       /* Find merge bases */
+       bases = get_merge_bases(local, remote, 1);
+       if (!bases) {
+               base_sha1 = null_sha1;
+               OUTPUT(o, 4, "No merge base found; doing history-less merge");
+       } else if (!bases->next) {
+               base_sha1 = bases->item->object.sha1;
+               OUTPUT(o, 4, "One merge base found (%.7s)",
+                      sha1_to_hex(base_sha1));
+       } else {
+               /* TODO: How to handle multiple merge-bases? */
+               base_sha1 = bases->item->object.sha1;
+               OUTPUT(o, 3, "Multiple merge bases found. Using the first "
+                      "(%.7s)", sha1_to_hex(base_sha1));
+       }
+
+       OUTPUT(o, 4, "Merging remote commit %.7s into local commit %.7s with "
+              "merge-base %.7s", sha1_to_hex(remote->object.sha1),
+              sha1_to_hex(local->object.sha1), sha1_to_hex(base_sha1));
+
+       if (!hashcmp(remote->object.sha1, base_sha1)) {
+               /* Already merged; result == local commit */
+               OUTPUT(o, 2, "Already up-to-date!");
+               hashcpy(result_sha1, local->object.sha1);
+               goto found_result;
+       }
+       if (!hashcmp(local->object.sha1, base_sha1)) {
+               /* Fast-forward; result == remote commit */
+               OUTPUT(o, 2, "Fast-forward");
+               hashcpy(result_sha1, remote->object.sha1);
+               goto found_result;
+       }
+
+       /* TODO: */
+       result = error("notes_merge() cannot yet handle real merges.");
+
+found_result:
+       free_commit_list(bases);
+       trace_printf("notes_merge(): result = %i, result_sha1 = %.7s\n",
+              result, sha1_to_hex(result_sha1));
+       return result;
+}