[PATCH 4/6] hook: support reordering of hook list

[Emily Shaffer <emilyshaffer@google.com>]

It's possible that in most cases a user wants to run pre-commit hook
'A', but in exactly one repo that user wants to run pre-commit hook 'A'
first instead. Teach 'git hook' to support this by allowing a user to
specify a new order number for a hook after the initial hook has been
specified.

For example:

  $ grep -A2 "\[hook\]" ~/.gitconfig
  [hook]
          pre-commit = 001:~/test.sh
          pre-commit = 999:~/baz.sh
  $ grep -A2 "\[hook\]" ~/git/.git/config
  [hook]
          pre-commit = 900:~/bar.sh
          pre-commit = 050:~/baz.sh
  $ ./bin-wrappers/git hook --list pre-commit
  001     global  ~/test.sh
  050     repo    ~/baz.sh
  900     repo    ~/bar.sh

In the above example, '~/baz.sh' is provided in the global config with
order position 999. Then, in the local config, that order is overridden
to 050. Instead of running ~/baz.sh twice (at order 050 and at order
999), only run it once, in the position specified last in config order.

Signed-off-by: Emily Shaffer <emilyshaffer@google.com>
---
 Documentation/git-hook.txt    |  8 ++++++++
 hook.c                        |  7 +++++++
 t/t1360-config-based-hooks.sh | 14 ++++++++++++++
 3 files changed, 29 insertions(+)

diff --git a/Documentation/git-hook.txt b/Documentation/git-hook.txt
index a141884239..0f7115f826 100644
--- a/Documentation/git-hook.txt
+++ b/Documentation/git-hook.txt
@@ -20,6 +20,14 @@ This command parses the default configuration files for lines which look like
 single hook. Hooks are sorted in ascending order by order number; in the event
 of an order number conflict, they are sorted in configuration order.
 
+The order number of a hook can be changed at a more local scope, e.g.:
+
+  git config --add --global hook.pre-commit "001:/foo.sh"
+  git config --add --local hook.pre-commit "005:/foo.sh"
+
+When the order number is respecified this way, the previously specified hook
+configuration is overridden.
+
 OPTIONS
 -------
 
diff --git a/hook.c b/hook.c
index f8d1109084..a7dcd18a2e 100644
--- a/hook.c
+++ b/hook.c
@@ -64,6 +64,13 @@ static int check_config_for_hooks(const char *var, const char *value, void *hook
 				emplace_hook(pos, order, command);
 				added = 1;
 			}
+
+			/*
+			 * if the command already exists, this entry should be
+			 * replacing it.
+			 */
+			if (!strcmp(item->command.buf, command))
+				remove_hook(pos);
 		}
 
 		if (!added)
diff --git a/t/t1360-config-based-hooks.sh b/t/t1360-config-based-hooks.sh
index 1434051db3..1af43ef18d 100755
--- a/t/t1360-config-based-hooks.sh
+++ b/t/t1360-config-based-hooks.sh
@@ -47,4 +47,18 @@ test_expect_success 'order number collisions resolved in config order' '
 	test_cmp expected actual
 '
 
+test_expect_success 'adding a command with a different number reorders list' '
+	cat >expected <<-\EOF &&
+	010	repo	/path/abc
+	050	repo	/path/def
+	100	repo	/path/ghi
+	990	repo	/path/rst
+	999	global	/path/uvw
+	EOF
+
+	git config --add --local hook.pre-commit "050:/path/def" &&
+	git hook --list pre-commit >actual &&
+	test_cmp expected actual
+'
+
 test_done
-- 
2.24.0.393.g34dc348eaf-goog