[PATCH 1/1] branch: advise the user to checkout a different branch before deleting

["Heba Waly via GitGitGadget" <gitgitgadget@gmail.com>]

From: Heba Waly <heba.waly@gmail.com>

Display a hint to the user when attempting to delete a checked out
branch saying "Checkout another branch before deleting this one:
git checkout <branch_name>".

Currently the user gets an error message saying: "error: Cannot delete
branch <branch_name> checked out at <path>". The hint will be displayed
after the error message.

Signed-off-by: Heba Waly <heba.waly@gmail.com>
---
 builtin/branch.c  | 2 ++
 t/t3200-branch.sh | 3 ++-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/builtin/branch.c b/builtin/branch.c
index d8297f80ff..799e967008 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -240,6 +240,8 @@ static int delete_branches(int argc, const char **argv, int force, int kinds,
 				error(_("Cannot delete branch '%s' "
 					"checked out at '%s'"),
 				      bname.buf, wt->path);
+				advise(_("Checkout another branch before deleting this "
+						 "one: git checkout <branch_name>"));
 				ret = 1;
 				continue;
 			}
diff --git a/t/t3200-branch.sh b/t/t3200-branch.sh
index 411a70b0ce..3b2812a8f4 100755
--- a/t/t3200-branch.sh
+++ b/t/t3200-branch.sh
@@ -808,7 +808,8 @@ test_expect_success 'test deleting branch without config' '
 test_expect_success 'deleting currently checked out branch fails' '
 	git worktree add -b my7 my7 &&
 	test_must_fail git -C my7 branch -d my7 &&
-	test_must_fail git branch -d my7 &&
+	test_must_fail git branch -d my7 >actual.out 2>actual.err &&
+	test_i18ngrep "hint: Checkout another branch" actual.err &&
 	rm -r my7 &&
 	git worktree prune
 '
-- 
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