[PATCH 5/5] checkout: do not die when leaving broken detached HEAD

[Jeff King <peff@peff.net>]

If we move away from a detached HEAD that has broken or
corrupted commits, we might die in two places:

  1. Printing the "old HEAD was..." message.

  2. Printing the list of orphaned commits.

In both cases, we ignore the return value of parse_commit
and feed the resulting commit to the pretty-print machinery,
which will die() upon failing to read the commit object
itself.

Since both cases are ancillary to the real operation being
performed, let's be more robust and keep going. This lets
user more easily checkout away from broken history.

Note that the call in describe_detached_head is also used to
describe the new commit we are moving to. We would want to
die in that case, but that is already handled much earlier,
when we parse the commit to get the tree to move to.

Signed-off-by: Jeff King <peff@peff.net>
---
 builtin/checkout.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 34a2e43..1df55c0 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -380,8 +380,8 @@ static void describe_detached_head(const char *msg, struct commit *commit)
 static void describe_detached_head(const char *msg, struct commit *commit)
 {
 	struct strbuf sb = STRBUF_INIT;
-	parse_commit(commit);
-	pp_commit_easy(CMIT_FMT_ONELINE, commit, &sb);
+	if (!parse_commit(commit))
+		pp_commit_easy(CMIT_FMT_ONELINE, commit, &sb);
 	fprintf(stderr, "%s %s... %s\n", msg,
 		find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV), sb.buf);
 	strbuf_release(&sb);
@@ -677,12 +677,12 @@ static void describe_one_orphan(struct strbuf *sb, struct commit *commit)
 
 static void describe_one_orphan(struct strbuf *sb, struct commit *commit)
 {
-	parse_commit(commit);
 	strbuf_addstr(sb, "  ");
 	strbuf_addstr(sb,
 		find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
 	strbuf_addch(sb, ' ');
-	pp_commit_easy(CMIT_FMT_ONELINE, commit, sb);
+	if (!parse_commit(commit))
+		pp_commit_easy(CMIT_FMT_ONELINE, commit, sb);
 	strbuf_addch(sb, '\n');
 }
 
-- 
1.8.4.1.4.gf327177