[PATCH 2/2] branch: support for at-refs like @{-1}

["Rubén Justo via GitGitGadget" <gitgitgadget@gmail.com>]

From: =?UTF-8?q?Rub=C3=A9n=20Justo?= <rjusto@gmail.com>

branch command with --edit-description, --set-upstream-to and
--unset-upstream options expects a branch name. A branch can be
specified using at-refs like @{-1}, so those references need to
be resolved.

We can modify the description of the previously checked out branch
with:

$ git branch --edit--description @{-1}

We can modify the upstream of the previously checked out branch
with:

$ git branch --set-upstream-to upstream @{-1}
$ git branch --unset-upstream @{-1}

Signed-off-by: Rubén Justo <rjusto@gmail.com>
---
 builtin/branch.c                      | 32 +++++++++++++++++++-----
 t/t3204-branch-name-interpretation.sh | 36 +++++++++++++++++++++++++++
 2 files changed, 62 insertions(+), 6 deletions(-)

diff --git a/builtin/branch.c b/builtin/branch.c
index 5229cb796f8..df620bee748 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -791,14 +791,17 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 	} else if (edit_description) {
 		const char *branch_name;
 		struct strbuf branch_ref = STRBUF_INIT;
+		struct strbuf buf = STRBUF_INIT;
 		int ret = 0;
 
 		if (!argc) {
 			if (filter.detached)
 				die(_("Cannot give description to detached HEAD"));
 			branch_name = head;
-		} else if (argc == 1)
-			branch_name = argv[0];
+		} else if (argc == 1) {
+			strbuf_branchname(&buf, argv[0], INTERPRET_BRANCH_LOCAL);
+			branch_name = buf.buf;
+		}
 		else
 			die(_("cannot edit description of more than one branch"));
 
@@ -814,6 +817,7 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 			ret = edit_branch_description(branch_name);
 
 		strbuf_release(&branch_ref);
+		strbuf_release(&buf);
 		return ret;
 	} else if (copy) {
 		if (!argc)
@@ -834,11 +838,19 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 		else
 			die(_("too many arguments for a rename operation"));
 	} else if (new_upstream) {
-		struct branch *branch = branch_get(argv[0]);
+		struct branch *branch;
+		struct strbuf buf = STRBUF_INIT;
 
-		if (argc > 1)
+		if (!argc)
+			branch = branch_get(NULL);
+		else if (argc == 1) {
+			strbuf_branchname(&buf, argv[0], INTERPRET_BRANCH_LOCAL);
+			branch = branch_get(buf.buf);
+		}
+		else
 			die(_("too many arguments to set new upstream"));
 
+
 		if (!branch) {
 			if (!argc || !strcmp(argv[0], "HEAD"))
 				die(_("could not set upstream of HEAD to %s when "
@@ -853,11 +865,18 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 		dwim_and_setup_tracking(the_repository, branch->name,
 					new_upstream, BRANCH_TRACK_OVERRIDE,
 					quiet);
+		strbuf_release(&buf);
 	} else if (unset_upstream) {
-		struct branch *branch = branch_get(argv[0]);
+		struct branch *branch;
 		struct strbuf buf = STRBUF_INIT;
 
-		if (argc > 1)
+		if (!argc)
+			branch = branch_get(NULL);
+		else if (argc == 1) {
+			strbuf_branchname(&buf, argv[0], INTERPRET_BRANCH_LOCAL);
+			branch = branch_get(buf.buf);
+		}
+		else
 			die(_("too many arguments to unset upstream"));
 
 		if (!branch) {
@@ -870,6 +889,7 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 		if (!branch_has_merge_config(branch))
 			die(_("Branch '%s' has no upstream information"), branch->name);
 
+		strbuf_reset(&buf);
 		strbuf_addf(&buf, "branch.%s.remote", branch->name);
 		git_config_set_multivar(buf.buf, NULL, NULL, CONFIG_FLAGS_MULTI_REPLACE);
 		strbuf_reset(&buf);
diff --git a/t/t3204-branch-name-interpretation.sh b/t/t3204-branch-name-interpretation.sh
index 993a6b5eff7..853315ec20a 100755
--- a/t/t3204-branch-name-interpretation.sh
+++ b/t/t3204-branch-name-interpretation.sh
@@ -133,4 +133,40 @@ test_expect_success 'checkout does not treat remote @{upstream} as a branch' '
 	expect_branch HEAD one
 '
 
+test_expect_success 'edit-description via @{-1}' '
+	git checkout main &&
+	git checkout - &&
+	write_script editor <<-\EOF &&
+		echo "Branch description" >"$1"
+	EOF
+	EDITOR=./editor git branch --edit-description @{-1} &&
+		write_script editor <<-\EOF &&
+		git stripspace -s <"$1" >"EDITOR_OUTPUT"
+	EOF
+	EDITOR=./editor git branch --edit-description @{-1} &&
+	echo "Branch description" >expect &&
+	test_cmp expect EDITOR_OUTPUT
+'
+
+test_expect_success 'modify branch upstream via "@{-1}@{upstream}"' "
+	cat >expect <<-\EOF &&
+	warning: not setting branch 'upstream-branch' as its own upstream
+	EOF
+	git branch upstream-branch &&
+	git checkout -b upstream-other -t upstream-branch &&
+	git checkout - &&
+	git branch --set-upstream-to upstream-branch @{-1}@{upstream} 2>actual &&
+	test_cmp expect actual
+"
+
+test_expect_success 'unset branch upstream via "@{-1}"' "
+	test "$(git config branch.upstream-other.remote)" = "." &&
+	test "$(git config branch.upstream-other.merge)" = "refs/heads/upstream-branch" &&
+	git checkout upstream-other &&
+	git checkout - &&
+	git branch --unset-upstream @{-1} &&
+	test_must_fail git config branch.upstream-other.remote &&
+	test_must_fail git config branch.upstream-other.merge
+"
+
 test_done
-- 
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