commit: fix a segfault when displaying a commit with unreachable parents

I was running git show on various commits found by fsck-objects
when I found this bug.  Since find_unique_abbrev() cannot find
an abbreviation for an object not in the database, it will
return NULL, which is bad to run strlen() on.  So instead, we'll
just display the unabbreviated sha1 that we referenced in the
commit.

I'm not sure that this is the best 'fix' for it because the
commit I was trying to show was broken, but I don't think a
program should segfault even if the user tries to do something
stupid.

Signed-off-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/commit.c b/commit.c
index 5b6e082c85f203cf27ac5b50f2d06a18b36fdc70..a6d543eee7831cd6a479d4cf8b2ba81a1438b298 100644 (file)
--- a/commit.c
+++ b/commit.c
@@ -548,10 +548,13 @@ static int add_merge_info(enum cmit_fmt fmt, char *buf, const struct commit *com
 
        while (parent) {
                struct commit *p = parent->item;
-               const char *hex = abbrev
-                       ? find_unique_abbrev(p->object.sha1, abbrev)
-                       : sha1_to_hex(p->object.sha1);
-               const char *dots = (abbrev && strlen(hex) != 40) ? "..." : "";
+               const char *hex = NULL;
+               const char *dots;
+               if (abbrev)
+                       hex = find_unique_abbrev(p->object.sha1, abbrev);
+               if (!hex)
+                       hex = sha1_to_hex(p->object.sha1);
+               dots = (abbrev && strlen(hex) != 40) ?  "..." : "";
                parent = parent->next;
 
                offset += sprintf(buf + offset, " %s%s", hex, dots);