git-rev-list: use proper lazy reachability analysis

This mean sthat you can give a beginning/end pair to git-rev-list,
and it will show all entries that are reachable from the beginning
but not the end.

For example

	git-rev-list v2.6.12-rc5 v2.6.12-rc4

shows all commits that are in -rc5 but are not in -rc4.

diff --git a/rev-list.c b/rev-list.c
index 93bee19..cb1de39 100644 (file)
--- a/rev-list.c
+++ b/rev-list.c
@@ -1,6 +1,10 @@
 #include "cache.h"
 #include "commit.h"
 
+#define SEEN           (1u << 0)
+#define INTERESTING    (1u << 1)
+#define UNINTERESTING  (1u << 2)
+
 static const char rev_list_usage[] =
        "usage: git-rev-list [OPTION] commit-id <commit-id>\n"
                      "  --max-count=nr\n"
@@ -8,6 +12,29 @@ static const char rev_list_usage[] =
                      "  --min-age=epoch\n"
                      "  --header";
 
+static void mark_parents_uninteresting(struct commit *commit)
+{
+       struct commit_list *parents = commit->parents;
+
+       while (parents) {
+               struct commit *commit = parents->item;
+               commit->object.flags |= UNINTERESTING;
+               parents = parents->next;
+       }
+}
+
+static int everybody_uninteresting(struct commit_list *list)
+{
+       while (list) {
+               struct commit *commit = list->item;
+               list = list->next;
+               if (commit->object.flags & UNINTERESTING)
+                       continue;
+               return 0;
+       }
+       return 1;
+}
+
 int main(int argc, char **argv)
 {
        int nr_sha;
@@ -60,11 +87,29 @@ int main(int argc, char **argv)
        }
 
        commit_list_insert(commit, &list);
-       do {
-               struct commit *commit = pop_most_recent_commit(&list, 0x1);
+       if (end) {
+               struct commit_list *newlist = NULL;
+               struct commit_list **p = &newlist;
+               do {
+                       struct commit *commit = pop_most_recent_commit(&list, SEEN);
+                       struct object *obj = &commit->object;
 
-               if (commit == end)
-                       break;
+                       if (commit == end || (obj->flags & UNINTERESTING)) {
+                               mark_parents_uninteresting(commit);
+                               if (everybody_uninteresting(list))
+                                       break;
+                               continue;
+                       }
+                       p = &commit_list_insert(commit, p)->next;
+               } while (list);
+               list = newlist;
+       }
+
+       while (list) {
+               struct commit *commit = pop_most_recent_commit(&list, SEEN);
+
+               if (commit->object.flags & UNINTERESTING)
+                       continue;
                if (min_age != -1 && (commit->date > min_age))
                        continue;
                if (max_age != -1 && (commit->date < max_age))
@@ -74,6 +119,6 @@ int main(int argc, char **argv)
                printf("%s\n", sha1_to_hex(commit->object.sha1));
                if (verbose_header)
                        printf("%s%c", commit->buffer, 0);
-       } while (list);
+       }
        return 0;
 }