From 6098817fd7f64209664c701df30096dc0f4fb876 Mon Sep 17 00:00:00 2001
From: Michael J Gruber <git@drmicha.warpmail.net>
Date: Wed, 7 Aug 2019 11:57:07 -0700
Subject: git-merge: honor pre-merge-commit hook
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

git-merge does not honor the pre-commit hook when doing automatic merge
commits, and for compatibility reasons this is going to stay.

Introduce a pre-merge-commit hook which is called for an automatic merge
commit just like pre-commit is called for a non-automatic merge commit
(or any other commit).

[js: * renamed hook from "pre-merge" to "pre-merge-commit"
     * only discard the index if the hook is actually present
     * expanded githooks documentation entry
     * clarified that hook should write messages to stderr
     * squashed test changes from the original series' patch 4/4
     * modified tests to follow new pattern from this series' patch 1/4
     * added a test case for non-executable merge hooks
     * added a test case for failed merges
     * when testing that the merge hook did not run, make sure we
       actually have a merge to perform (by resetting the "side" branch
       to its original state).
     * reworded commit message
]

Improved-by: Martin Ågren <martin.agren@gmail.com>
Signed-off-by: Michael J Gruber <git@grubix.eu>
Signed-off-by: Martin Ågren <martin.agren@gmail.com>
Signed-off-by: Josh Steadmon <steadmon@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/githooks.txt b/Documentation/githooks.txt
index 82cd573..d9da474 100644
--- a/Documentation/githooks.txt
+++ b/Documentation/githooks.txt
@@ -103,6 +103,27 @@ The default 'pre-commit' hook, when enabled--and with the
 `hooks.allownonascii` config option unset or set to false--prevents
 the use of non-ASCII filenames.
 
+pre-merge-commit
+~~~~~~~~~~~~~~~~
+
+This hook is invoked by linkgit:git-merge[1]. It takes no parameters, and is
+invoked after the merge has been carried out successfully and before
+obtaining the proposed commit log message to
+make a commit.  Exiting with a non-zero status from this script
+causes the `git merge` command to abort before creating a commit.
+
+The default 'pre-merge-commit' hook, when enabled, runs the
+'pre-commit' hook, if the latter is enabled.
+
+This hook is invoked with the environment variable
+`GIT_EDITOR=:` if the command will not bring up an editor
+to modify the commit message.
+
+If the merge cannot be carried out automatically, the conflicts
+need to be resolved and the result committed separately (see
+linkgit:git-merge[1]). At that point, this hook will not be executed,
+but the 'pre-commit' hook will, if it is enabled.
+
 prepare-commit-msg
 ~~~~~~~~~~~~~~~~~~
 
diff --git a/builtin/merge.c b/builtin/merge.c
index 4425a7a..bf0ae68 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -816,6 +816,18 @@ static void write_merge_heads(struct commit_list *);
 static void prepare_to_commit(struct commit_list *remoteheads)
 {
 	struct strbuf msg = STRBUF_INIT;
+	const char *index_file = get_index_file();
+
+	if (run_commit_hook(0 < option_edit, index_file, "pre-merge-commit", NULL))
+		abort_commit(remoteheads, NULL);
+	/*
+	 * Re-read the index as pre-merge-commit hook could have updated it,
+	 * and write it out as a tree.  We must do this before we invoke
+	 * the editor and after we invoke run_status above.
+	 */
+	if (find_hook("pre-merge-commit"))
+		discard_cache();
+	read_cache_from(index_file);
 	strbuf_addbuf(&msg, &merge_msg);
 	if (squash)
 		BUG("the control must not reach here under --squash");
diff --git a/t/t7503-pre-commit-and-pre-merge-commit-hooks.sh b/t/t7503-pre-commit-and-pre-merge-commit-hooks.sh
new file mode 100755
index 0000000..7a5434c
--- /dev/null
+++ b/t/t7503-pre-commit-and-pre-merge-commit-hooks.sh
@@ -0,0 +1,242 @@
+#!/bin/sh
+
+test_description='pre-commit and pre-merge-commit hooks'
+
+. ./test-lib.sh
+
+HOOKDIR="$(git rev-parse --git-dir)/hooks"
+PRECOMMIT="$HOOKDIR/pre-commit"
+PREMERGE="$HOOKDIR/pre-merge-commit"
+
+# Prepare sample scripts that write their $0 to actual_hooks
+test_expect_success 'sample script setup' '
+	mkdir -p "$HOOKDIR" &&
+	write_script "$HOOKDIR/success.sample" <<-\EOF &&
+	echo $0 >>actual_hooks
+	exit 0
+	EOF
+	write_script "$HOOKDIR/fail.sample" <<-\EOF &&
+	echo $0 >>actual_hooks
+	exit 1
+	EOF
+	write_script "$HOOKDIR/non-exec.sample" <<-\EOF &&
+	echo $0 >>actual_hooks
+	exit 1
+	EOF
+	chmod -x "$HOOKDIR/non-exec.sample" &&
+	write_script "$HOOKDIR/require-prefix.sample" <<-\EOF &&
+	echo $0 >>actual_hooks
+	test $GIT_PREFIX = "success/"
+	EOF
+	write_script "$HOOKDIR/check-author.sample" <<-\EOF
+	echo $0 >>actual_hooks
+	test "$GIT_AUTHOR_NAME" = "New Author" &&
+	test "$GIT_AUTHOR_EMAIL" = "newauthor@example.com"
+	EOF
+'
+
+test_expect_success 'root commit' '
+	echo "root" >file &&
+	git add file &&
+	git commit -m "zeroth" &&
+	git checkout -b side &&
+	echo "foo" >foo &&
+	git add foo &&
+	git commit -m "make it non-ff" &&
+	git branch side-orig side &&
+	git checkout master
+'
+
+test_expect_success 'setup conflicting branches' '
+	test_when_finished "git checkout master" &&
+	git checkout -b conflicting-a master &&
+	echo a >conflicting &&
+	git add conflicting &&
+	git commit -m conflicting-a &&
+	git checkout -b conflicting-b master &&
+	echo b >conflicting &&
+	git add conflicting &&
+	git commit -m conflicting-b
+'
+
+test_expect_success 'with no hook' '
+	test_when_finished "rm -f actual_hooks" &&
+	echo "foo" >file &&
+	git add file &&
+	git commit -m "first" &&
+	test_path_is_missing actual_hooks
+'
+
+test_expect_success 'with no hook (merge)' '
+	test_when_finished "rm -f actual_hooks" &&
+	git branch -f side side-orig &&
+	git checkout side &&
+	git merge -m "merge master" master &&
+	git checkout master &&
+	test_path_is_missing actual_hooks
+'
+
+test_expect_success '--no-verify with no hook' '
+	test_when_finished "rm -f actual_hooks" &&
+	echo "bar" >file &&
+	git add file &&
+	git commit --no-verify -m "bar" &&
+	test_path_is_missing actual_hooks
+'
+
+test_expect_success 'with succeeding hook' '
+	test_when_finished "rm -f \"$PRECOMMIT\" expected_hooks actual_hooks" &&
+	cp "$HOOKDIR/success.sample" "$PRECOMMIT" &&
+	echo "$PRECOMMIT" >expected_hooks &&
+	echo "more" >>file &&
+	git add file &&
+	git commit -m "more" &&
+	test_cmp expected_hooks actual_hooks
+'
+
+test_expect_success 'with succeeding hook (merge)' '
+	test_when_finished "rm -f \"$PREMERGE\" expected_hooks actual_hooks" &&
+	cp "$HOOKDIR/success.sample" "$PREMERGE" &&
+	echo "$PREMERGE" >expected_hooks &&
+	git checkout side &&
+	git merge -m "merge master" master &&
+	git checkout master &&
+	test_cmp expected_hooks actual_hooks
+'
+
+test_expect_success 'automatic merge fails; both hooks are available' '
+	test_when_finished "rm -f \"$PREMERGE\" \"$PRECOMMIT\"" &&
+	test_when_finished "rm -f expected_hooks actual_hooks" &&
+	test_when_finished "git checkout master" &&
+	cp "$HOOKDIR/success.sample" "$PREMERGE" &&
+	cp "$HOOKDIR/success.sample" "$PRECOMMIT" &&
+
+	git checkout conflicting-a &&
+	test_must_fail git merge -m "merge conflicting-b" conflicting-b &&
+	test_path_is_missing actual_hooks &&
+
+	echo "$PRECOMMIT" >expected_hooks &&
+	echo a+b >conflicting &&
+	git add conflicting &&
+	git commit -m "resolve conflict" &&
+	test_cmp expected_hooks actual_hooks
+'
+
+test_expect_success '--no-verify with succeeding hook' '
+	test_when_finished "rm -f \"$PRECOMMIT\" actual_hooks" &&
+	cp "$HOOKDIR/success.sample" "$PRECOMMIT" &&
+	echo "even more" >>file &&
+	git add file &&
+	git commit --no-verify -m "even more" &&
+	test_path_is_missing actual_hooks
+'
+
+test_expect_success 'with failing hook' '
+	test_when_finished "rm -f \"$PRECOMMIT\" expected_hooks actual_hooks" &&
+	cp "$HOOKDIR/fail.sample" "$PRECOMMIT" &&
+	echo "$PRECOMMIT" >expected_hooks &&
+	echo "another" >>file &&
+	git add file &&
+	test_must_fail git commit -m "another" &&
+	test_cmp expected_hooks actual_hooks
+'
+
+test_expect_success '--no-verify with failing hook' '
+	test_when_finished "rm -f \"$PRECOMMIT\" actual_hooks" &&
+	cp "$HOOKDIR/fail.sample" "$PRECOMMIT" &&
+	echo "stuff" >>file &&
+	git add file &&
+	git commit --no-verify -m "stuff" &&
+	test_path_is_missing actual_hooks
+'
+
+test_expect_success 'with failing hook (merge)' '
+	test_when_finished "rm -f \"$PREMERGE\" expected_hooks actual_hooks" &&
+	cp "$HOOKDIR/fail.sample" "$PREMERGE" &&
+	echo "$PREMERGE" >expected_hooks &&
+	git checkout side &&
+	test_must_fail git merge -m "merge master" master &&
+	git checkout master &&
+	test_cmp expected_hooks actual_hooks
+'
+
+test_expect_success POSIXPERM 'with non-executable hook' '
+	test_when_finished "rm -f \"$PRECOMMIT\" actual_hooks" &&
+	cp "$HOOKDIR/non-exec.sample" "$PRECOMMIT" &&
+	echo "content" >>file &&
+	git add file &&
+	git commit -m "content" &&
+	test_path_is_missing actual_hooks
+'
+
+test_expect_success POSIXPERM '--no-verify with non-executable hook' '
+	test_when_finished "rm -f \"$PRECOMMIT\" actual_hooks" &&
+	cp "$HOOKDIR/non-exec.sample" "$PRECOMMIT" &&
+	echo "more content" >>file &&
+	git add file &&
+	git commit --no-verify -m "more content" &&
+	test_path_is_missing actual_hooks
+'
+
+test_expect_success POSIXPERM 'with non-executable hook (merge)' '
+	test_when_finished "rm -f \"$PREMERGE\" actual_hooks" &&
+	cp "$HOOKDIR/non-exec.sample" "$PREMERGE" &&
+	git branch -f side side-orig &&
+	git checkout side &&
+	git merge -m "merge master" master &&
+	git checkout master &&
+	test_path_is_missing actual_hooks
+'
+
+test_expect_success 'with hook requiring GIT_PREFIX' '
+	test_when_finished "rm -rf \"$PRECOMMIT\" expected_hooks actual_hooks success" &&
+	cp "$HOOKDIR/require-prefix.sample" "$PRECOMMIT" &&
+	echo "$PRECOMMIT" >expected_hooks &&
+	echo "more content" >>file &&
+	git add file &&
+	mkdir success &&
+	(
+		cd success &&
+		git commit -m "hook requires GIT_PREFIX = success/"
+	) &&
+	test_cmp expected_hooks actual_hooks
+'
+
+test_expect_success 'with failing hook requiring GIT_PREFIX' '
+	test_when_finished "rm -rf \"$PRECOMMIT\" expected_hooks actual_hooks fail" &&
+	cp "$HOOKDIR/require-prefix.sample" "$PRECOMMIT" &&
+	echo "$PRECOMMIT" >expected_hooks &&
+	echo "more content" >>file &&
+	git add file &&
+	mkdir fail &&
+	(
+		cd fail &&
+		test_must_fail git commit -m "hook must fail"
+	) &&
+	git checkout -- file &&
+	test_cmp expected_hooks actual_hooks
+'
+
+test_expect_success 'check the author in hook' '
+	test_when_finished "rm -f \"$PRECOMMIT\" expected_hooks actual_hooks" &&
+	cp "$HOOKDIR/check-author.sample" "$PRECOMMIT" &&
+	cat >expected_hooks <<-EOF &&
+	$PRECOMMIT
+	$PRECOMMIT
+	$PRECOMMIT
+	EOF
+	test_must_fail git commit --allow-empty -m "by a.u.thor" &&
+	(
+		GIT_AUTHOR_NAME="New Author" &&
+		GIT_AUTHOR_EMAIL="newauthor@example.com" &&
+		export GIT_AUTHOR_NAME GIT_AUTHOR_EMAIL &&
+		git commit --allow-empty -m "by new.author via env" &&
+		git show -s
+	) &&
+	git commit --author="New Author <newauthor@example.com>" \
+		--allow-empty -m "by new.author via command line" &&
+	git show -s &&
+	test_cmp expected_hooks actual_hooks
+'
+
+test_done
diff --git a/t/t7503-pre-commit-hook.sh b/t/t7503-pre-commit-hook.sh
deleted file mode 100755
index 6aa8320..0000000
--- a/t/t7503-pre-commit-hook.sh
+++ /dev/null
@@ -1,160 +0,0 @@
-#!/bin/sh
-
-test_description='pre-commit hook'
-
-. ./test-lib.sh
-
-HOOKDIR="$(git rev-parse --git-dir)/hooks"
-PRECOMMIT="$HOOKDIR/pre-commit"
-
-# Prepare sample scripts that write their $0 to actual_hooks
-test_expect_success 'sample script setup' '
-	mkdir -p "$HOOKDIR" &&
-	write_script "$HOOKDIR/success.sample" <<-\EOF &&
-	echo $0 >>actual_hooks
-	exit 0
-	EOF
-	write_script "$HOOKDIR/fail.sample" <<-\EOF &&
-	echo $0 >>actual_hooks
-	exit 1
-	EOF
-	write_script "$HOOKDIR/non-exec.sample" <<-\EOF &&
-	echo $0 >>actual_hooks
-	exit 1
-	EOF
-	chmod -x "$HOOKDIR/non-exec.sample" &&
-	write_script "$HOOKDIR/require-prefix.sample" <<-\EOF &&
-	echo $0 >>actual_hooks
-	test $GIT_PREFIX = "success/"
-	EOF
-	write_script "$HOOKDIR/check-author.sample" <<-\EOF
-	echo $0 >>actual_hooks
-	test "$GIT_AUTHOR_NAME" = "New Author" &&
-	test "$GIT_AUTHOR_EMAIL" = "newauthor@example.com"
-	EOF
-'
-
-test_expect_success 'with no hook' '
-	test_when_finished "rm -f actual_hooks" &&
-	echo "foo" >file &&
-	git add file &&
-	git commit -m "first" &&
-	test_path_is_missing actual_hooks
-'
-
-test_expect_success '--no-verify with no hook' '
-	test_when_finished "rm -f actual_hooks" &&
-	echo "bar" >file &&
-	git add file &&
-	git commit --no-verify -m "bar" &&
-	test_path_is_missing actual_hooks
-'
-
-test_expect_success 'with succeeding hook' '
-	test_when_finished "rm -f \"$PRECOMMIT\" expected_hooks actual_hooks" &&
-	cp "$HOOKDIR/success.sample" "$PRECOMMIT" &&
-	echo "$PRECOMMIT" >expected_hooks &&
-	echo "more" >>file &&
-	git add file &&
-	git commit -m "more" &&
-	test_cmp expected_hooks actual_hooks
-'
-
-test_expect_success '--no-verify with succeeding hook' '
-	test_when_finished "rm -f \"$PRECOMMIT\" actual_hooks" &&
-	cp "$HOOKDIR/success.sample" "$PRECOMMIT" &&
-	echo "even more" >>file &&
-	git add file &&
-	git commit --no-verify -m "even more" &&
-	test_path_is_missing actual_hooks
-'
-
-test_expect_success 'with failing hook' '
-	test_when_finished "rm -f \"$PRECOMMIT\" expected_hooks actual_hooks" &&
-	cp "$HOOKDIR/fail.sample" "$PRECOMMIT" &&
-	echo "$PRECOMMIT" >expected_hooks &&
-	echo "another" >>file &&
-	git add file &&
-	test_must_fail git commit -m "another" &&
-	test_cmp expected_hooks actual_hooks
-'
-
-test_expect_success '--no-verify with failing hook' '
-	test_when_finished "rm -f \"$PRECOMMIT\" actual_hooks" &&
-	cp "$HOOKDIR/fail.sample" "$PRECOMMIT" &&
-	echo "stuff" >>file &&
-	git add file &&
-	git commit --no-verify -m "stuff" &&
-	test_path_is_missing actual_hooks
-'
-
-test_expect_success POSIXPERM 'with non-executable hook' '
-	test_when_finished "rm -f \"$PRECOMMIT\" actual_hooks" &&
-	cp "$HOOKDIR/non-exec.sample" "$PRECOMMIT" &&
-	echo "content" >>file &&
-	git add file &&
-	git commit -m "content" &&
-	test_path_is_missing actual_hooks
-'
-
-test_expect_success POSIXPERM '--no-verify with non-executable hook' '
-	test_when_finished "rm -f \"$PRECOMMIT\" actual_hooks" &&
-	cp "$HOOKDIR/non-exec.sample" "$PRECOMMIT" &&
-	echo "more content" >>file &&
-	git add file &&
-	git commit --no-verify -m "more content" &&
-	test_path_is_missing actual_hooks
-'
-
-test_expect_success 'with hook requiring GIT_PREFIX' '
-	test_when_finished "rm -rf \"$PRECOMMIT\" expected_hooks actual_hooks success" &&
-	cp "$HOOKDIR/require-prefix.sample" "$PRECOMMIT" &&
-	echo "$PRECOMMIT" >expected_hooks &&
-	echo "more content" >>file &&
-	git add file &&
-	mkdir success &&
-	(
-		cd success &&
-		git commit -m "hook requires GIT_PREFIX = success/"
-	) &&
-	test_cmp expected_hooks actual_hooks
-'
-
-test_expect_success 'with failing hook requiring GIT_PREFIX' '
-	test_when_finished "rm -rf \"$PRECOMMIT\" expected_hooks actual_hooks fail" &&
-	cp "$HOOKDIR/require-prefix.sample" "$PRECOMMIT" &&
-	echo "$PRECOMMIT" >expected_hooks &&
-	echo "more content" >>file &&
-	git add file &&
-	mkdir fail &&
-	(
-		cd fail &&
-		test_must_fail git commit -m "hook must fail"
-	) &&
-	git checkout -- file &&
-	test_cmp expected_hooks actual_hooks
-'
-
-test_expect_success 'check the author in hook' '
-	test_when_finished "rm -f \"$PRECOMMIT\" expected_hooks actual_hooks" &&
-	cp "$HOOKDIR/check-author.sample" "$PRECOMMIT" &&
-	cat >expected_hooks <<-EOF &&
-	$PRECOMMIT
-	$PRECOMMIT
-	$PRECOMMIT
-	EOF
-	test_must_fail git commit --allow-empty -m "by a.u.thor" &&
-	(
-		GIT_AUTHOR_NAME="New Author" &&
-		GIT_AUTHOR_EMAIL="newauthor@example.com" &&
-		export GIT_AUTHOR_NAME GIT_AUTHOR_EMAIL &&
-		git commit --allow-empty -m "by new.author via env" &&
-		git show -s
-	) &&
-	git commit --author="New Author <newauthor@example.com>" \
-		--allow-empty -m "by new.author via command line" &&
-	git show -s &&
-	test_cmp expected_hooks actual_hooks
-'
-
-test_done
diff --git a/templates/hooks--pre-merge-commit.sample b/templates/hooks--pre-merge-commit.sample
new file mode 100755
index 0000000..399eab1
--- /dev/null
+++ b/templates/hooks--pre-merge-commit.sample
@@ -0,0 +1,13 @@
+#!/bin/sh
+#
+# An example hook script to verify what is about to be committed.
+# Called by "git merge" with no arguments.  The hook should
+# exit with non-zero status after issuing an appropriate message to
+# stderr if it wants to stop the merge commit.
+#
+# To enable this hook, rename this file to "pre-merge-commit".
+
+. git-sh-setup
+test -x "$GIT_DIR/hooks/pre-commit" &&
+        exec "$GIT_DIR/hooks/pre-commit"
+:
-- 
cgit v0.10.2-6-g49f6