Subject: [PATCH v3 0/3] config: allow overriding global/system config

From: Patrick Steinhardt <[email-masked]>
Date: Mon, 12 Apr 2021 16:46:37 +0200

Hi,

this is the third version of my patch series to provide a way of
overriding the global system configuration.

Changes compared to v2:

    - `/dev/null` is now truly special-cased to skip reading any file
      such that it's possible to use it e.g. in environments where this
      special file does not exist.

    - There is no explicit requirement for the given files to exist
      anymore. On the reading side, it will in most cases just be
      ignored (except for e.g. `git config --global --list` and similar,
      where we'd also fail if the normal global config didn't exist). On
      the writing site, we now create the config file it it's missing.

    - Both `git_system_config()` and `git_global_config()` now pass
      memory ownership to the caller.

Patrick

Patrick Steinhardt (3):
  config: rename `git_etc_config()`
  config: unify code paths to get global config paths
  config: allow overriding of global and system configuration

 Documentation/git-config.txt |  5 +++
 Documentation/git.txt        | 10 +++++
 builtin/config.c             | 12 ++++--
 config.c                     | 48 ++++++++++++++++++------
 config.h                     |  4 +-
 t/t1300-config.sh            | 71 ++++++++++++++++++++++++++++++++++++
 6 files changed, 133 insertions(+), 17 deletions(-)

Range-diff against v2:
1:  da0b8ce6f0 ! 1:  34bdbc27d6 config: rename `git_etc_config()`
    @@ Commit message
         would start to become misleading.
     
         Rename the function to `git_system_config()` as a preparatory step.
    +    While at it, the function is also refactored to pass memory ownership to
    +    the caller. This is done to better match semantics of
    +    `git_global_config()`, which is going to be introduced in the next
    +    commit.
     
         Signed-off-by: Patrick Steinhardt <[email-masked]>
     
    @@ config.c: static int git_config_from_blob_ref(config_fn_t fn,
      }
      
     -const char *git_etc_gitconfig(void)
    -+const char *git_system_config(void)
    ++char *git_system_config(void)
      {
    - 	static const char *system_wide;
    - 	if (!system_wide)
    +-	static const char *system_wide;
    +-	if (!system_wide)
    +-		system_wide = system_path(ETC_GITCONFIG);
    +-	return system_wide;
    ++	return system_path(ETC_GITCONFIG);
    + }
    + 
    + /*
    +@@ config.c: static int do_git_config_sequence(const struct config_options *opts,
    + 				  config_fn_t fn, void *data)
    + {
    + 	int ret = 0;
    ++	char *system_config = git_system_config();
    + 	char *xdg_config = xdg_config_home("config");
    + 	char *user_config = expand_user_path("~/.gitconfig", 0);
    + 	char *repo_config;
     @@ config.c: static int do_git_config_sequence(const struct config_options *opts,
      		repo_config = NULL;
      
      	current_parsing_scope = CONFIG_SCOPE_SYSTEM;
     -	if (git_config_system() && !access_or_die(git_etc_gitconfig(), R_OK,
    -+	if (git_config_system() && !access_or_die(git_system_config(), R_OK,
    - 						  opts->system_gently ?
    - 						  ACCESS_EACCES_OK : 0))
    +-						  opts->system_gently ?
    +-						  ACCESS_EACCES_OK : 0))
     -		ret += git_config_from_file(fn, git_etc_gitconfig(),
    -+		ret += git_config_from_file(fn, git_system_config(),
    - 					    data);
    +-					    data);
    ++	if (system_config && !access_or_die(system_config, R_OK,
    ++					    opts->system_gently ?
    ++					    ACCESS_EACCES_OK : 0))
    ++		ret += git_config_from_file(fn, system_config, data);
      
      	current_parsing_scope = CONFIG_SCOPE_GLOBAL;
    + 	if (xdg_config && !access_or_die(xdg_config, R_OK, ACCESS_EACCES_OK))
    +@@ config.c: static int do_git_config_sequence(const struct config_options *opts,
    + 		die(_("unable to parse command-line config"));
    + 
    + 	current_parsing_scope = prev_parsing_scope;
    ++	free(system_config);
    + 	free(xdg_config);
    + 	free(user_config);
    + 	free(repo_config);
     
      ## config.h ##
     @@ config.h: int git_config_rename_section(const char *, const char *);
    @@ config.h: int config_error_nonbool(const char *);
      #define config_error_nonbool(s) (config_error_nonbool(s), const_error())
      #endif
      
    -+const char *git_system_config(void);
    ++char *git_system_config(void);
     +
      int git_config_parse_parameter(const char *, config_fn_t fn, void *data);
      
2:  dddc85bcf5 < -:  ---------- config: unify code paths to get global config paths
-:  ---------- > 2:  30f18679bd config: unify code paths to get global config paths
3:  272a3b31aa ! 3:  af663640ae config: allow overriding of global and system configuration
    @@ Commit message
         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_NOSYSTEM`
    -    as an equivalent to `GIT_CONFIG_NOGLOBAL`. But in the past, it has
    +    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`
    @@ Commit message
             - 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. This path must
    -          exist and be readable to ensure that the user didn't typo.
    +          configuration files and instead take the path.
     
             - If set to `/dev/null`, we do not load either global- or
               system-level configuration at all.
    @@ Documentation/git.txt: for further details.
     +`GIT_CONFIG_GLOBAL`::
     +`GIT_CONFIG_SYSTEM`::
     +	Take the configuration from the given files instead from global or
    -+	system-level configuration files. The files must exist and be readable
    -+	by the current user. If `GIT_CONFIG_SYSTEM` is set, `/etc/gitconfig`
    ++	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
    @@ Documentation/git.txt: for further details.
      	Whether to skip reading settings from the system-wide
      	`$(prefix)/etc/gitconfig` file.  This environment variable can
     
    + ## builtin/config.c ##
    +@@ builtin/config.c: int cmd_config(int argc, const char **argv, const char *prefix)
    + 		char *user_config, *xdg_config;
    + 
    + 		git_global_config(&user_config, &xdg_config);
    +-		if (!user_config)
    ++		if (!user_config) {
    ++			if (getenv("GIT_CONFIG_GLOBAL"))
    ++				die(_("GIT_CONFIG_GLOBAL=/dev/null set"));
    ++
    + 			/*
    + 			 * It is unknown if HOME/.gitconfig exists, so
    + 			 * we do not know if we should write to XDG
    +@@ builtin/config.c: int cmd_config(int argc, const char **argv, const char *prefix)
    + 			 * is set and points at a sane location.
    + 			 */
    + 			die(_("$HOME not set"));
    ++		}
    + 
    + 		given_config_source.scope = CONFIG_SCOPE_GLOBAL;
    + 
    +
      ## config.c ##
     @@ config.c: static int git_config_from_blob_ref(config_fn_t fn,
    - const char *git_system_config(void)
    + 
    + char *git_system_config(void)
      {
    - 	static const char *system_wide;
    --	if (!system_wide)
    --		system_wide = system_path(ETC_GITCONFIG);
    -+
    -+	if (!system_wide) {
    -+		system_wide = xstrdup_or_null(getenv("GIT_CONFIG_SYSTEM"));
    -+		if (system_wide) {
    -+			/*
    -+			 * If GIT_CONFIG_SYSTEM is set, it overrides the
    -+			 * /etc/gitconfig. Furthermore, the file must exist in
    -+			 * order to prevent any typos by the user.
    -+			 */
    -+			if (access(system_wide, R_OK))
    -+				die(_("cannot access '%s'"), system_wide);
    -+		} else {
    -+			system_wide = system_path(ETC_GITCONFIG);
    -+		}
    ++	char *system_config = xstrdup_or_null(getenv("GIT_CONFIG_SYSTEM"));
    ++	if (system_config) {
    ++		if (!strcmp(system_config, "/dev/null"))
    ++			FREE_AND_NULL(system_config);
    ++		return system_config;
     +	}
    -+
    - 	return system_wide;
    + 	return system_path(ETC_GITCONFIG);
      }
      
    -@@ config.c: void git_global_config(const char **user, const char **xdg)
    - 	static const char *user_config, *xdg_config;
    +-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) {
    ++		if (!strcmp(user_config, "/dev/null"))
    ++			FREE_AND_NULL(user_config);
    ++		xdg_config = NULL;
    ++	} else {
    ++		user_config = expand_user_path("~/.gitconfig", 0);
    ++		xdg_config = xdg_config_home("config");
    ++	}
    ++
    ++	*user_out = user_config;
    ++	*xdg_out = xdg_config;
    + }
      
    - 	if (!user_config) {
    --		user_config = expand_user_path("~/.gitconfig", 0);
    --		xdg_config = xdg_config_home("config");
    -+		user_config = xstrdup_or_null(getenv("GIT_CONFIG_GLOBAL"));
    -+		if (user_config) {
    -+			/*
    -+			 * If GIT_CONFIG_GLOBAL is set, then it overrides both
    -+			 * the ~/.gitconfig and the XDG configuration file.
    -+			 * Furthermore, the file must exist in order to prevent
    -+			 * any typos by the user.
    -+			 */
    -+			if (access(user_config, R_OK))
    -+				die(_("cannot access '%s'"), user_config);
    -+		} else {
    -+			user_config = expand_user_path("~/.gitconfig", 0);
    -+			xdg_config = xdg_config_home("config");
    -+		}
    - 	}
    - 
    - 	*user = user_config;
    + /*
     
      ## t/t1300-config.sh ##
     @@ t/t1300-config.sh: test_expect_success '--show-scope with --show-origin' '
    @@ t/t1300-config.sh: test_expect_success '--show-scope with --show-origin' '
     +
     +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 version &&
    -+	test_must_fail env GIT_CONFIG_SYSTEM=does-not-exist git version &&
    -+	GIT_CONFIG_NOSYSTEM=true GIT_CONFIG_SYSTEM=does-not-exist git version
    ++	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' '
    @@ t/t1300-config.sh: test_expect_success '--show-scope with --show-origin' '
     +	key = value
     +EOF
     +
    -+	test_must_fail env GIT_CONFIG_GLOBAL=write-to-global git config --global config.key value &&
    -+	touch write-to-global &&
     +	GIT_CONFIG_GLOBAL=write-to-global git config --global config.key value &&
     +	test_cmp expect write-to-global &&
     +
    -+	test_must_fail env GIT_CONFIG_SYSTEM=write-to-system git config --system config.key value &&
    -+	touch write-to-system &&
     +	GIT_CONFIG_SYSTEM=write-to-system git config --system config.key value &&
     +	test_cmp expect write-to-system
     +'
-- 
2.31.1