[PATCH 2/3] config: add GIT_CONFIG_INCLUDES

["Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>]

From: Derrick Stolee <stolee@gmail.com>

The config keys 'include.path' and 'includeIf.*' allow users to specify
config stored in a location outside of the typical list of config files
(system, global, local, etc.). For example, users who accept the risk
can specify helpful aliases via a file checked into the repo by pointing
'include.path' to the position of that file in the working directory.
This is dangerous, but people do it.

What becomes tricky is that this modifies all Git behavior, including
operations that are intended to be limited in activity or sandboxed in
some way. These include directives can provide surprising changes to
behavior, especially when expecting a specific list of allowed file
accesses. This could lead to failed builds, for instance.

To allow for these user-desired features when they are running commands,
add a new GIT_CONFIG_INCLUDES environment variable that disables these
redirections of config when set to zero. This variable can be set by
automation, such as build tooling, to avoid these strange behaviors.
This could be considered a recommended option for tools executing Git
commands, the same as GIT_ADVICE=0.

Signed-off-by: Derrick Stolee <stolee@gmail.com>
---
 Documentation/git-config.adoc |  5 +++++
 config.c                      |  7 ++++++-
 environment.h                 |  6 ++++++
 t/t1305-config-include.sh     | 31 +++++++++++++++++++++++++++++++
 4 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/Documentation/git-config.adoc b/Documentation/git-config.adoc
index 044d776613..c9b5159501 100644
--- a/Documentation/git-config.adoc
+++ b/Documentation/git-config.adoc
@@ -502,6 +502,11 @@ GIT_CONFIG::
 	historical compatibility; there is generally no reason to use it
 	instead of the `--file` option.
 
+GIT_CONFIG_INCLUDES::
+	If GIT_CONFIG_INCLUDES is set to 0, then Git will not follow
+	`include.path` or `includeIf.*.path` directives when reading
+	configuration files.
+
 [[EXAMPLES]]
 EXAMPLES
 --------
diff --git a/config.c b/config.c
index a1b92fe083..85edd05672 100644
--- a/config.c
+++ b/config.c
@@ -1595,9 +1595,14 @@ int config_with_options(config_fn_t fn, void *data,
 			const struct config_options *opts)
 {
 	struct config_include_data inc = CONFIG_INCLUDE_INIT;
+	int respect_includes = opts->respect_includes;
 	int ret;
 
-	if (opts->respect_includes) {
+	if (respect_includes &&
+	    !git_env_bool(CONFIG_INCLUDES_ENVIRONMENT, 1))
+		respect_includes = 0;
+
+	if (respect_includes) {
 		inc.fn = fn;
 		inc.data = data;
 		inc.opts = opts;
diff --git a/environment.h b/environment.h
index 9eb97b3869..2c57ae2533 100644
--- a/environment.h
+++ b/environment.h
@@ -52,6 +52,12 @@
  */
 #define GIT_ADVICE_ENVIRONMENT "GIT_ADVICE"
 
+/*
+ * Environment variable used to prevent following include.path or includeIf.*
+ * config directives.
+ */
+#define CONFIG_INCLUDES_ENVIRONMENT "GIT_CONFIG_INCLUDES"
+
 /*
  * Environment variable used in handshaking the wire protocol.
  * Contains a colon ':' separated list of keys with optional values
diff --git a/t/t1305-config-include.sh b/t/t1305-config-include.sh
index f3892578e4..270e4b89ab 100755
--- a/t/t1305-config-include.sh
+++ b/t/t1305-config-include.sh
@@ -396,4 +396,35 @@ test_expect_success 'onbranch without repository but explicit nonexistent Git di
 	test_must_fail nongit git --git-dir=nonexistent config get foo.bar
 '
 
+test_expect_success 'GIT_CONFIG_INCLUDES=0 disables include.path and includeIf' '
+	test_when_finished "rm -rf repo" &&
+	git init repo &&
+	(
+		cd repo &&
+		git config set include.path config.inc &&
+		git config set "includeIf.gitdir:*.path" config2.inc &&
+		git config set -f .git/config.inc foo.bar from-include &&
+		git config set -f .git/config2.inc foo.baz from-includeif &&
+		git config get foo.bar &&
+		git config get foo.baz &&
+		test_must_fail env GIT_CONFIG_INCLUDES=0 git config get foo.bar &&
+		test_must_fail env GIT_CONFIG_INCLUDES=0 git config get foo.baz &&
+		git config get --includes foo.bar &&
+		test_must_fail env GIT_CONFIG_INCLUDES=0 git config get --includes foo.bar
+	)
+'
+
+test_expect_success 'GIT_CONFIG_INCLUDES=0 blocks included alias override' '
+	test_when_finished "rm -rf repo" &&
+	git init repo &&
+	(
+		cd repo &&
+		git config set alias.test false &&
+		git config set include.path config.inc &&
+		git config set -f .git/config.inc alias.test status &&
+		git test &&
+		test_must_fail env GIT_CONFIG_INCLUDES=0 git test
+	)
+'
+
 test_done
-- 
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