trailer: add new .cmd config option

The `trailer.<token>.command` configuration variable
specifies a command (run via the shell, so it does not have
to be a single name or path to the command, but can be a
shell script), and the first occurrence of substring $ARG is
replaced with the value given to the `interpret-trailer`
command for the token in a '--trailer <token>=<value>' argument.

This has three downsides:

* The use of $ARG in the mechanism misleads the users that
the value is passed in the shell variable, and tempt them
to use $ARG more than once, but that would not work, as
the second and subsequent $ARG are not replaced.

* Because $ARG is textually replaced without regard to the
shell language syntax, even '$ARG' (inside a single-quote
pair), which a user would expect to stay intact, would be
replaced, and worse, if the value had an unmatched single
quote (imagine a name like "O'Connor", substituted into
NAME='$ARG' to make it NAME='O'Connor'), it would result in
a broken command that is not syntactically correct (or
worse).

* The first occurrence of substring `$ARG` will be replaced
with the empty string, in the command when the command is
first called to add a trailer with the specified <token>.
This is a bad design, the nature of automatic execution
causes it to add a trailer that we don't expect.

Introduce a new `trailer.<token>.cmd` configuration that
takes higher precedence to deprecate and eventually remove
`trailer.<token>.command`, which passes the value as an
argument to the command.  Instead of "$ARG", users can
refer to the value as positional argument, $1, in their
scripts. At the same time, in order to allow
`git interpret-trailers` to better simulate the behavior
of `git command -s`, 'trailer.<token>.cmd' will not
automatically execute.

Helped-by: Junio C Hamano <gitster@pobox.com>
Helped-by: Christian Couder <christian.couder@gmail.com>
Signed-off-by: ZheNing Hu <adlternative@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 84 insertions, 0 deletions

diff --git a/t/t7513-interpret-trailers.sh b/t/t7513-interpret-trailers.sh
index 6602790..04885d0 100755
--- a/t/t7513-interpret-trailers.sh
+++ b/t/t7513-interpret-trailers.sh
@@ -51,6 +51,69 @@ test_expect_success 'setup' '
 	EOF
 '
 
+test_expect_success 'with cmd' '
+	test_when_finished "git config --remove-section trailer.bug" &&
+	git config trailer.bug.key "Bug-maker: " &&
+	git config trailer.bug.ifExists "add" &&
+	git config trailer.bug.cmd "echo \"maybe is\"" &&
+	cat >expected2 <<-EOF &&
+
+	Bug-maker: maybe is him
+	Bug-maker: maybe is me
+	EOF
+	git interpret-trailers --trailer "bug: him" --trailer "bug:me" \
+		>actual2 &&
+	test_cmp expected2 actual2
+'
+
+test_expect_success 'with cmd and $1' '
+	test_when_finished "git config --remove-section trailer.bug" &&
+	git config trailer.bug.key "Bug-maker: " &&
+	git config trailer.bug.ifExists "add" &&
+	git config trailer.bug.cmd "echo \"\$1\" is" &&
+	cat >expected2 <<-EOF &&
+
+	Bug-maker: him is him
+	Bug-maker: me is me
+	EOF
+	git interpret-trailers --trailer "bug: him" --trailer "bug:me" \
+		>actual2 &&
+	test_cmp expected2 actual2
+'
+
+test_expect_success 'with cmd and $1 with sh -c' '
+	test_when_finished "git config --remove-section trailer.bug" &&
+	git config trailer.bug.key "Bug-maker: " &&
+	git config trailer.bug.ifExists "replace" &&
+	git config trailer.bug.cmd "sh -c \"echo who is \"\$1\"\"" &&
+	cat >expected2 <<-EOF &&
+
+	Bug-maker: who is me
+	EOF
+	git interpret-trailers --trailer "bug: him" --trailer "bug:me" \
+		>actual2 &&
+	test_cmp expected2 actual2
+'
+
+test_expect_success 'with cmd and $1 with shell script' '
+	test_when_finished "git config --remove-section trailer.bug" &&
+	git config trailer.bug.key "Bug-maker: " &&
+	git config trailer.bug.ifExists "replace" &&
+	git config trailer.bug.cmd "./echoscript" &&
+	cat >expected2 <<-EOF &&
+
+	Bug-maker: who is me
+	EOF
+	cat >echoscript <<-EOF &&
+	#!/bin/sh
+	echo who is "\$1"
+	EOF
+	chmod +x echoscript &&
+	git interpret-trailers --trailer "bug: him" --trailer "bug:me" \
+		>actual2 &&
+	test_cmp expected2 actual2
+'
+
 test_expect_success 'without config' '
 	sed -e "s/ Z\$/ /" >expected <<-\EOF &&
 
@@ -1274,6 +1337,27 @@ test_expect_success 'setup a commit' '
 	git commit -m "Add file a.txt"
 '
 
+test_expect_success 'cmd takes precedence over command' '
+	test_when_finished "git config --unset trailer.fix.cmd" &&
+	git config trailer.fix.ifExists "replace" &&
+	git config trailer.fix.cmd "test -n \"\$1\" && git log -1 --oneline --format=\"%h (%aN)\" \
+	--abbrev-commit --abbrev=14 \"\$1\" || true" &&
+	git config trailer.fix.command "git log -1 --oneline --format=\"%h (%s)\" \
+		--abbrev-commit --abbrev=14 \$ARG" &&
+	FIXED=$(git log -1 --oneline --format="%h (%aN)" --abbrev-commit --abbrev=14 HEAD) &&
+	cat complex_message_body >expected2 &&
+	sed -e "s/ Z\$/ /" >>expected2 <<-EOF &&
+		Fixes: $FIXED
+		Acked-by= Z
+		Reviewed-by:
+		Signed-off-by: Z
+		Signed-off-by: A U Thor <author@example.com>
+	EOF
+	git interpret-trailers --trailer "review:" --trailer "fix=HEAD" \
+		<complex_message >actual2 &&
+	test_cmp expected2 actual2
+'
+
 test_expect_success 'with command using $ARG' '
 	git config trailer.fix.ifExists "replace" &&
 	git config trailer.fix.command "git log -1 --oneline --format=\"%h (%s)\" --abbrev-commit --abbrev=14 \$ARG" &&