[PATCH v4] branch: let '--edit-description' default to rebased/bisected branch

[marcandre.lureau@redhat.com]

From: Marc-André Lureau <marcandre.lureau@redhat.com>

Defaulting to editing the description of the rebased or bisected branch
without an explicit branchname argument would be useful.  Even the git
bash prompt shows the name of the rebased branch, and then

  ~/src/git (mybranch|REBASE-i 1/2)$ git branch --edit-description
  fatal: Cannot give description to detached HEAD

looks quite unhelpful.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
Changed in v4:
 - use wt_status_get_state() that handles bisect state
 - add a bisecting test

builtin/branch.c  | 41 ++++++++++++++++++++++++++++++-----------
 t/t3200-branch.sh | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 65 insertions(+), 11 deletions(-)

diff --git a/builtin/branch.c b/builtin/branch.c
index d8297f80ff..cda9fd53e6 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -745,33 +745,52 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 		string_list_clear(&output, 0);
 		return 0;
 	} else if (edit_description) {
-		const char *branch_name;
+		char *branch_name = NULL;
 		struct strbuf branch_ref = STRBUF_INIT;
 
 		if (!argc) {
-			if (filter.detached)
-				die(_("Cannot give description to detached HEAD"));
-			branch_name = head;
+			if (!filter.detached)
+				branch_name = xstrdup(head);
+			else {
+				struct wt_status_state state;
+
+				memset(&state, 0, sizeof(state));
+				wt_status_get_state(the_repository, &state, 0);
+				branch_name = state.branch;
+				if (!branch_name)
+					die(_("Cannot give description to detached HEAD"));
+				free(state.onto);
+				free(state.detached_from);
+			}
 		} else if (argc == 1)
-			branch_name = argv[0];
+			branch_name = xstrdup(argv[0]);
 		else
 			die(_("cannot edit description of more than one branch"));
 
 		strbuf_addf(&branch_ref, "refs/heads/%s", branch_name);
 		if (!ref_exists(branch_ref.buf)) {
-			strbuf_release(&branch_ref);
+			int ret;
 
 			if (!argc)
-				return error(_("No commit on branch '%s' yet."),
-					     branch_name);
+				ret = error(_("No commit on branch '%s' yet."),
+					    branch_name);
 			else
-				return error(_("No branch named '%s'."),
-					     branch_name);
+				ret = error(_("No branch named '%s'."),
+					    branch_name);
+
+			strbuf_release(&branch_ref);
+			free(branch_name);
+			return ret;
+
 		}
 		strbuf_release(&branch_ref);
 
-		if (edit_branch_description(branch_name))
+		if (edit_branch_description(branch_name)) {
+			free(branch_name);
 			return 1;
+		}
+
+		free(branch_name);
 	} else if (copy) {
 		if (!argc)
 			die(_("branch name required"));
diff --git a/t/t3200-branch.sh b/t/t3200-branch.sh
index 411a70b0ce..7ea6876fe7 100755
--- a/t/t3200-branch.sh
+++ b/t/t3200-branch.sh
@@ -1260,6 +1260,41 @@ test_expect_success 'use --edit-description' '
 	test_cmp expect EDITOR_OUTPUT
 '
 
+test_expect_success 'use --edit-description during rebase' '
+	write_script editor <<-\EOF &&
+		echo "Rebase contents" >"$1"
+	EOF
+	(
+		set_fake_editor &&
+		FAKE_LINES="break 1" git rebase -i HEAD^ &&
+		EDITOR=./editor git branch --edit-description &&
+		git rebase --continue
+	) &&
+	write_script editor <<-\EOF &&
+		git stripspace -s <"$1" >"EDITOR_OUTPUT"
+	EOF
+	EDITOR=./editor git branch --edit-description &&
+	echo "Rebase contents" >expect &&
+	test_cmp expect EDITOR_OUTPUT
+'
+
+test_expect_success 'use --edit-description during bisect' '
+	write_script editor <<-\EOF &&
+		echo "Bisect contents" >"$1"
+	EOF
+	git bisect start &&
+	git bisect bad &&
+	git bisect good HEAD~2 &&
+	EDITOR=./editor git branch --edit-description &&
+	git bisect reset &&
+	write_script editor <<-\EOF &&
+		git stripspace -s <"$1" >"EDITOR_OUTPUT"
+	EOF
+	EDITOR=./editor git branch --edit-description &&
+	echo "Bisect contents" >expect &&
+	test_cmp expect EDITOR_OUTPUT
+'
+
 test_expect_success 'detect typo in branch name when using --edit-description' '
 	write_script editor <<-\EOF &&
 		echo "New contents" >"$1"

base-commit: 7a6a90c6ec48fc78c83d7090d6c1b95d8f3739c0
-- 
2.25.0.rc2.1.ga00adf396b.dirty