Do a very simple "merge-base" that finds the most recent common

[git.git] / merge-base.c

diff --git a/merge-base.c b/merge-base.c
new file mode 100644 (file)
index 0000000..36ac420
--- /dev/null
+++ b/merge-base.c
@@ -0,0 +1,57 @@
+#include "cache.h"
+#include "revision.h"
+
+/*
+ * This is stupid. We could have much better heurstics, I bet.
+ */
+static int better(struct revision *new, struct revision *old)
+{
+       return new->date > old->date;
+}
+
+static struct revision *common_parent(struct revision *rev1, struct revision *rev2)
+{
+       int i;
+       struct revision *best = NULL;
+
+       mark_reachable(rev1, 1);
+       mark_reachable(rev2, 2);
+       for (i = 0; i < nr_revs ;i++) {
+               struct revision *rev = revs[i];
+               if ((rev->flags & 3) != 3)
+                       continue;
+               if (!best) {
+                       best = rev;
+                       continue;
+               }
+               if (better(rev, best))
+                       best = rev;
+       }
+       return best;
+}
+
+int main(int argc, char **argv)
+{
+       unsigned char rev1[20], rev2[20];
+       struct revision *common;
+
+       if (argc != 3 || get_sha1_hex(argv[1], rev1) || get_sha1_hex(argv[2], rev2))
+               usage("merge-base <commit1> <commit2>");
+
+       /*
+        * We will eventually want to include a revision cache file
+        * that "rev-tree.c" has generated, since this is going to
+        * otherwise be quite expensive for big trees..
+        *
+        * That's some time off, though, and in the meantime we know
+        * that we have a solution to the eventual expense.
+        */
+       parse_commit(rev1);
+       parse_commit(rev2);
+
+       common = common_parent(lookup_rev(rev1), lookup_rev(rev2));
+       if (!common)
+               die("no common parent found");
+       printf("%s\n", sha1_to_hex(common->sha1));
+       return 0;
+}