[PATCH v2 11/11] rebase: dereference tags

["Phillip Wood via GitGitGadget" <gitgitgadget@xxxxxxxxx>]

From: Phillip Wood <phillip.wood@xxxxxxxxxxxxx>

Aborting a rebase stated with 'git rebase <upstream> <tag-object>'
should checkout the commit pointed to by <tag-object>. Instead it gives

    error: update_ref failed for ref 'HEAD': cannot update ref 'HEAD':
    trying to write non-commit object
    710d743b2b9892457fdcc3970f397e6ec07447e0 to branch 'HEAD'

This is because when we parse the command line arguments although we
check that the tag points to a commit we remember the oid of the tag
and try and checkout that object rather than the commit it points
to. Fix this by using lookup_commit_reference_by_name() when parsing
the command line.

Signed-off-by: Phillip Wood <phillip.wood@xxxxxxxxxxxxx>
---
---
 builtin/rebase.c        | 14 ++++++++------
 t/t3407-rebase-abort.sh | 18 ++++++++++++++----
 2 files changed, 22 insertions(+), 10 deletions(-)

diff --git a/builtin/rebase.c b/builtin/rebase.c
index 74663208468..2b70a196f9a 100644
--- a/builtin/rebase.c
+++ b/builtin/rebase.c
@@ -1903,13 +1903,15 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 			die_if_checked_out(buf.buf, 1);
 			options.head_name = xstrdup(buf.buf);
 		/* If not is it a valid ref (branch or commit)? */
-		} else if (!get_oid(branch_name, &options.orig_head) &&
-			   lookup_commit_reference(the_repository,
-						   &options.orig_head))
+		} else {
+			struct commit *commit =
+				lookup_commit_reference_by_name(branch_name);
+			if (!commit)
+				die(_("no such branch/commit '%s'"),
+				    branch_name);
+			oidcpy(&options.orig_head, &commit->object.oid);
 			options.head_name = NULL;
-		else
-			die(_("no such branch/commit '%s'"),
-			    branch_name);
+		}
 	} else if (argc == 0) {
 		/* Do not need to switch branches, we are already on it. */
 		options.head_name =
diff --git a/t/t3407-rebase-abort.sh b/t/t3407-rebase-abort.sh
index 162112ba5ea..ebbaed147a6 100755
--- a/t/t3407-rebase-abort.sh
+++ b/t/t3407-rebase-abort.sh
@@ -11,18 +11,18 @@ test_expect_success setup '
 	test_commit a a a &&
 	git branch to-rebase &&
 
-	test_commit b a b &&
-	test_commit c a c &&
+	test_commit --annotate b a b &&
+	test_commit --annotate c a c &&
 
 	git checkout to-rebase &&
 	test_commit "merge should fail on this" a d d &&
-	test_commit "merge should fail on this, too" a e pre-rebase
+	test_commit --annotate "merge should fail on this, too" a e pre-rebase
 '
 
 # Check that HEAD is equal to "pre-rebase" and the current branch is
 # "to-rebase"
 check_head() {
-	test_cmp_rev HEAD pre-rebase &&
+	test_cmp_rev HEAD pre-rebase^{commit} &&
 	test "$(git symbolic-ref HEAD)" = refs/heads/to-rebase
 }
 
@@ -67,6 +67,16 @@ testrebase() {
 		test_path_is_missing "$state_dir"
 	'
 
+	test_expect_success "rebase$type --abort when checking out a tag" '
+		test_when_finished "git symbolic-ref HEAD refs/heads/to-rebase" &&
+		git reset --hard a -- &&
+		test_must_fail git rebase$type --onto b c pre-rebase &&
+		test_cmp_rev HEAD b^{commit} &&
+		git rebase --abort &&
+		test_cmp_rev HEAD pre-rebase^{commit} &&
+		! git symbolic-ref HEAD
+	'
+
 	test_expect_success "rebase$type --abort does not update reflog" '
 		# Clean up the state from the previous one
 		git reset --hard pre-rebase &&
-- 
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