[PATCH] commit: check return value of lookup_commit()

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

If lookup_commit() returns NULL, there's usually serious error and the
command aborts anyway. However it's still nicer to have a message
telling us where it aborts, rather than segmentation fault.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 I suppose die() also cleans up $GIT_DIR/index.lock while sigsegv does not.

 builtin/commit.c |   17 +++++++++++++----
 1 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/builtin/commit.c b/builtin/commit.c
index 2088b6b..bfb7a5a 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -1387,6 +1387,7 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 	unsigned char commit_sha1[20];
 	struct ref_lock *ref_lock;
 	struct commit_list *parents = NULL, **pptr = &parents;
+	struct commit *commit;
 	struct stat statbuf;
 	int allow_fast_forward = 1;
 	struct wt_status s;
@@ -1423,7 +1424,6 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 			reflog_msg = "commit (initial)";
 	} else if (amend) {
 		struct commit_list *c;
-		struct commit *commit;
 
 		if (!reflog_msg)
 			reflog_msg = "commit (amend)";
@@ -1439,7 +1439,10 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 
 		if (!reflog_msg)
 			reflog_msg = "commit (merge)";
-		pptr = &commit_list_insert(lookup_commit(head_sha1), pptr)->next;
+		commit = lookup_commit(head_sha1);
+		if (!commit)
+			die(_("could not parse HEAD commit"));
+		pptr = &commit_list_insert(commit, pptr)->next;
 		fp = fopen(git_path("MERGE_HEAD"), "r");
 		if (fp == NULL)
 			die_errno(_("could not open '%s' for reading"),
@@ -1448,7 +1451,10 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 			unsigned char sha1[20];
 			if (get_sha1_hex(m.buf, sha1) < 0)
 				die(_("Corrupt MERGE_HEAD file (%s)"), m.buf);
-			pptr = &commit_list_insert(lookup_commit(sha1), pptr)->next;
+			commit = lookup_commit(sha1);
+			if (!commit)
+				die(_("could not parse commit %s"), sha1_to_hex(sha1));
+			pptr = &commit_list_insert(commit, pptr)->next;
 		}
 		fclose(fp);
 		strbuf_release(&m);
@@ -1465,7 +1471,10 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 			reflog_msg = (whence == FROM_CHERRY_PICK)
 					? "commit (cherry-pick)"
 					: "commit";
-		pptr = &commit_list_insert(lookup_commit(head_sha1), pptr)->next;
+		commit = lookup_commit(head_sha1);
+		if (!commit)
+			die(_("could not parse HEAD commit"));
+		pptr = &commit_list_insert(commit, pptr)->next;
 	}
 
 	/* Finally, get the commit message */
-- 
1.7.4.74.g639db