[PATCH v3] branch: let '--edit-description' default to rebased branch during rebase

[marcandre.lureau@redhat.com]

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

Defaulting to editing the description of the rebased 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 v3:
 - fix memory leaks on error paths
 - remove test_done left-over
 - style fixes

builtin/branch.c  | 40 +++++++++++++++++++++++++++++-----------
 t/t3200-branch.sh | 18 ++++++++++++++++++
 2 files changed, 47 insertions(+), 11 deletions(-)

diff --git a/builtin/branch.c b/builtin/branch.c
index d8297f80ff..033a045d40 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -745,33 +745,51 @@ 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));
+				if (wt_status_check_rebase(NULL, &state))
+					branch_name = state.branch;
+				if (!branch_name)
+					die(_("Cannot give description to detached HEAD"));
+				free(state.onto);
+			}
 		} 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..d2bdaf324d 100755
--- a/t/t3200-branch.sh
+++ b/t/t3200-branch.sh
@@ -1260,6 +1260,24 @@ 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 'detect typo in branch name when using --edit-description' '
 	write_script editor <<-\EOF &&
 		echo "New contents" >"$1"

base-commit: 7a6a90c6ec48fc78c83d7090d6c1b95d8f3739c0
-- 
2.25.0.rc2.2.g5aece98438