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From: Patrick Steinhardt <ps@pks.im>
To: git@vger.kernel.org
Cc: "Junio C Hamano" <gitster@pobox.com>, "Jeff King" <peff@peff.net>,
	"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
	"Eric Sunshine" <sunshine@sunshineco.com>
Subject: [PATCH v4 3/3] config: allow overriding of global and system configuration
Date: Tue, 13 Apr 2021 09:11:52 +0200
Message-ID: <d27efc0aa847f3fb179307b3a265b3759b7d9570.1618297711.git.ps@pks.im> (raw)
In-Reply-To: <cover.1618297711.git.ps@pks.im>


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In order to have git run in a fully controlled environment without any
misconfiguration, it may be desirable for users or scripts to override
global- and system-level configuration files. We already have a way of
doing this, which is to unset both HOME and XDG_CONFIG_HOME environment
variables and to set `GIT_CONFIG_NOGLOBAL=true`. This is quite kludgy,
and unsetting the first two variables likely has an impact on other
executables spawned by such a script.

The obvious way to fix this would be to introduce `GIT_CONFIG_NOGLOBAL`
as an equivalent to `GIT_CONFIG_NOSYSTEM`. But in the past, it has
turned out that this design is inflexible: we cannot test system-level
parsing of the git configuration in our test harness because there is no
way to change its location, so all tests run with `GIT_CONFIG_NOSYSTEM`
set.

Instead of doing the same mistake with `GIT_CONFIG_NOGLOBAL`, introduce
two new variables `GIT_CONFIG_GLOBAL` and `GIT_CONFIG_SYSTEM`:

    - If unset, git continues to use the usual locations.

    - If set to a specific path, we skip reading the normal
      configuration files and instead take the path. By setting the path
      to `/dev/null`, no configuration will be loaded for the respective
      level.

This implements the usecase where we want to execute code in a sanitized
environment without any potential misconfigurations via `/dev/null`, but
is more flexible and allows for more usecases than simply adding
`GIT_CONFIG_NOGLOBAL`.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 Documentation/git-config.txt |  5 +++
 Documentation/git.txt        | 10 +++++
 config.c                     | 17 +++++++--
 t/t1300-config.sh            | 71 ++++++++++++++++++++++++++++++++++++
 4 files changed, 100 insertions(+), 3 deletions(-)

diff --git a/Documentation/git-config.txt b/Documentation/git-config.txt
index 4b4cc5c5e8..5cddadafd2 100644
--- a/Documentation/git-config.txt
+++ b/Documentation/git-config.txt
@@ -340,6 +340,11 @@ GIT_CONFIG::
 	Using the "--global" option forces this to ~/.gitconfig. Using the
 	"--system" option forces this to $(prefix)/etc/gitconfig.
 
+GIT_CONFIG_GLOBAL::
+GIT_CONFIG_SYSTEM::
+	Take the configuration from the given files instead from global or
+	system-level configuration. See linkgit:git[1] for details.
+
 GIT_CONFIG_NOSYSTEM::
 	Whether to skip reading settings from the system-wide
 	$(prefix)/etc/gitconfig file. See linkgit:git[1] for details.
diff --git a/Documentation/git.txt b/Documentation/git.txt
index 3a9c44987f..380422a6a9 100644
--- a/Documentation/git.txt
+++ b/Documentation/git.txt
@@ -670,6 +670,16 @@ for further details.
 	If this environment variable is set to `0`, git will not prompt
 	on the terminal (e.g., when asking for HTTP authentication).
 
+`GIT_CONFIG_GLOBAL`::
+`GIT_CONFIG_SYSTEM`::
+	Take the configuration from the given files instead from global or
+	system-level configuration files. If `GIT_CONFIG_SYSTEM` is set, the
+	system config file defined at build time (usually `/etc/gitconfig`)
+	will not be read. Likewise, if `GIT_CONFIG_GLOBAL` is set, neither
+	`$HOME/.gitconfig` nor `$XDG_CONFIG_HOME/git/config` will be read. Can
+	be set to `/dev/null` to skip reading configuration files of the
+	respective level.
+
 `GIT_CONFIG_NOSYSTEM`::
 	Whether to skip reading settings from the system-wide
 	`$(prefix)/etc/gitconfig` file.  This environment variable can
diff --git a/config.c b/config.c
index ebff58aa57..7caf6c1e53 100644
--- a/config.c
+++ b/config.c
@@ -1846,13 +1846,24 @@ static int git_config_from_blob_ref(config_fn_t fn,
 
 char *git_system_config(void)
 {
+	char *system_config = xstrdup_or_null(getenv("GIT_CONFIG_SYSTEM"));
+	if (system_config)
+		return system_config;
 	return system_path(ETC_GITCONFIG);
 }
 
-void git_global_config(char **user_config, char **xdg_config)
+void git_global_config(char **user_out, char **xdg_out)
 {
-	*user_config = expand_user_path("~/.gitconfig", 0);
-	*xdg_config = xdg_config_home("config");
+	char *user_config = xstrdup_or_null(getenv("GIT_CONFIG_GLOBAL"));
+	char *xdg_config = NULL;
+
+	if (!user_config) {
+		user_config = expand_user_path("~/.gitconfig", 0);
+		xdg_config = xdg_config_home("config");
+	}
+
+	*user_out = user_config;
+	*xdg_out = xdg_config;
 }
 
 /*
diff --git a/t/t1300-config.sh b/t/t1300-config.sh
index e0dd5d65ce..17f1b78c01 100755
--- a/t/t1300-config.sh
+++ b/t/t1300-config.sh
@@ -2059,6 +2059,77 @@ test_expect_success '--show-scope with --show-origin' '
 	test_cmp expect output
 '
 
+test_expect_success 'override global and system config' '
+	test_when_finished rm -f "$HOME"/.config/git &&
+
+	cat >"$HOME"/.gitconfig <<-EOF &&
+	[home]
+		config = true
+	EOF
+	mkdir -p "$HOME"/.config/git &&
+	cat >"$HOME"/.config/git/config <<-EOF &&
+	[xdg]
+		config = true
+	EOF
+	cat >.git/config <<-EOF &&
+	[local]
+		config = true
+	EOF
+	cat >custom-global-config <<-EOF &&
+	[global]
+		config = true
+	EOF
+	cat >custom-system-config <<-EOF &&
+	[system]
+		config = true
+	EOF
+
+	cat >expect <<-EOF &&
+	global	xdg.config=true
+	global	home.config=true
+	local	local.config=true
+	EOF
+	git config --show-scope --list >output &&
+	test_cmp expect output &&
+
+	sane_unset GIT_CONFIG_NOSYSTEM &&
+
+	cat >expect <<-EOF &&
+	system	system.config=true
+	global	global.config=true
+	local	local.config=true
+	EOF
+	GIT_CONFIG_SYSTEM=custom-system-config GIT_CONFIG_GLOBAL=custom-global-config \
+		git config --show-scope --list >output &&
+	test_cmp expect output &&
+
+	cat >expect <<-EOF &&
+	local	local.config=true
+	EOF
+	GIT_CONFIG_SYSTEM=/dev/null GIT_CONFIG_GLOBAL=/dev/null git config --show-scope --list >output &&
+	test_cmp expect output
+'
+
+test_expect_success 'override global and system config with missing file' '
+	sane_unset GIT_CONFIG_NOSYSTEM &&
+	test_must_fail env GIT_CONFIG_GLOBAL=does-not-exist GIT_CONFIG_SYSTEM=/dev/null git config --global --list >actual &&
+	test_must_fail env GIT_CONFIG_GLOBAL=/dev/null GIT_CONFIG_SYSTEM=does-not-exist git config --system --list >actual &&
+	GIT_CONFIG_GLOBAL=does-not-exist GIT_CONFIG_SYSTEM=does-not-exist git version
+'
+
+test_expect_success 'write to overridden global and system config' '
+	cat >expect <<EOF &&
+[config]
+	key = value
+EOF
+
+	GIT_CONFIG_GLOBAL=write-to-global git config --global config.key value &&
+	test_cmp expect write-to-global &&
+
+	GIT_CONFIG_SYSTEM=write-to-system git config --system config.key value &&
+	test_cmp expect write-to-system
+'
+
 for opt in --local --worktree
 do
 	test_expect_success "$opt requires a repo" '
-- 
2.31.1


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  parent reply index

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-08 14:17 [PATCH] config: Introduce GIT_CONFIG_NOGLOBAL Patrick Steinhardt
2021-04-08 16:44 ` Eric Sunshine
2021-04-08 17:25 ` Junio C Hamano
2021-04-08 23:18   ` Jeff King
2021-04-08 23:43     ` Junio C Hamano
2021-04-09  0:25       ` Jeff King
2021-04-08 23:34   ` Ævar Arnfjörð Bjarmason
2021-04-08 23:39   ` Ævar Arnfjörð Bjarmason
2021-04-08 23:30 ` Ævar Arnfjörð Bjarmason
2021-04-08 23:56   ` Junio C Hamano
2021-04-09 13:43 ` [PATCH v2 0/3] config: allow overriding global/system config Patrick Steinhardt
2021-04-09 13:43   ` [PATCH v2 1/3] config: rename `git_etc_config()` Patrick Steinhardt
2021-04-09 15:13     ` Jeff King
2021-04-09 13:43   ` [PATCH v2 2/3] config: unify code paths to get global config paths Patrick Steinhardt
2021-04-09 15:21     ` Jeff King
2021-04-09 13:43   ` [PATCH v2 3/3] config: allow overriding of global and system configuration Patrick Steinhardt
2021-04-09 15:38     ` Jeff King
2021-04-12 14:04       ` Patrick Steinhardt
2021-04-09 22:18     ` Junio C Hamano
2021-04-09 15:41   ` [PATCH v2 0/3] config: allow overriding global/system config Jeff King
2021-04-12 14:46   ` [PATCH v3 " Patrick Steinhardt
2021-04-12 14:46     ` [PATCH v3 1/3] config: rename `git_etc_config()` Patrick Steinhardt
2021-04-12 14:46     ` [PATCH v3 2/3] config: unify code paths to get global config paths Patrick Steinhardt
2021-04-12 14:46     ` [PATCH v3 3/3] config: allow overriding of global and system configuration Patrick Steinhardt
2021-04-12 17:04       ` Junio C Hamano
2021-04-13  7:11     ` [PATCH v4 0/3] config: allow overriding global/system config Patrick Steinhardt
2021-04-13  7:11       ` [PATCH v4 1/3] config: rename `git_etc_config()` Patrick Steinhardt
2021-04-13  7:25         ` Jeff King
2021-04-16 21:14         ` SZEDER Gábor
2021-04-17  8:44           ` Jeff King
2021-04-17 21:37             ` Junio C Hamano
2021-04-18  5:39               ` Jeff King
2021-04-19 11:03                 ` Patrick Steinhardt
2021-04-23  9:27                   ` Jeff King
2021-04-13  7:11       ` [PATCH v4 2/3] config: unify code paths to get global config paths Patrick Steinhardt
2021-04-13  7:11       ` Patrick Steinhardt [this message]
2021-04-13  7:33         ` [PATCH v4 3/3] config: allow overriding of global and system configuration Jeff King
2021-04-13  7:54           ` Patrick Steinhardt
2021-04-13  7:33       ` [PATCH v4 0/3] config: allow overriding global/system config Jeff King
2021-04-13 17:49       ` Junio C Hamano
2021-04-14  5:37         ` Patrick Steinhardt
2021-04-19 12:31       ` [PATCH v5 " Patrick Steinhardt
2021-04-19 12:31         ` [PATCH v5 1/3] config: rename `git_etc_config()` Patrick Steinhardt
2021-04-19 12:31         ` [PATCH v5 2/3] config: unify code paths to get global config paths Patrick Steinhardt
2021-04-19 12:31         ` [PATCH v5 3/3] config: allow overriding of global and system configuration Patrick Steinhardt
2021-04-21 20:46           ` SZEDER Gábor
2021-04-21 21:06             ` SZEDER Gábor
2021-04-22  5:36               ` Patrick Steinhardt
2021-04-23  5:47             ` [PATCH] t1300: fix unset of GIT_CONFIG_NOSYSTEM leaking into subsequent tests Patrick Steinhardt
2021-04-19 21:55         ` [PATCH v5 0/3] config: allow overriding global/system config Junio C Hamano
2021-04-23  9:32         ` Jeff King
2021-04-12 14:46 ` [PATCH v3] config: allow overriding of global and system configuration Patrick Steinhardt

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