[RFC PATCH 1/1] config: learn the "hostname:" includeIf condition

[Ignacio Encinas <ignacio@iencinas.com>]

Currently, customizing the configuration depending on the machine running
git has to be done manually.

Add support for a new includeIf keyword "hostname:" to conditionally
include configuration files depending on the hostname.

Signed-off-by: Ignacio Encinas <ignacio@iencinas.com>
---
 Documentation/config.txt  |  9 +++++++++
 config.c                  | 16 ++++++++++++++++
 t/t1305-config-include.sh | 22 ++++++++++++++++++++++
 3 files changed, 47 insertions(+)

diff --git a/Documentation/config.txt b/Documentation/config.txt
index e3a74dd1c1..9a22fd2609 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -186,6 +186,11 @@ As for the naming of this keyword, it is for forwards compatibility with
 a naming scheme that supports more variable-based include conditions,
 but currently Git only supports the exact keyword described above.
 
+`hostname`::
+	The data that follows the keyword `hostname:` is taken to be a
+	pattern with standard globbing wildcards. If the current
+	hostname matches the pattern, the include condition is met.
+
 A few more notes on matching via `gitdir` and `gitdir/i`:
 
  * Symlinks in `$GIT_DIR` are not resolved before matching.
@@ -261,6 +266,10 @@ Example
 	path = foo.inc
 [remote "origin"]
 	url = https://example.com/git
+
+; include only if the hostname of the machine matches some-hostname
+[includeIf "hostname:some-hostname"]
+	path = foo.inc
 ----
 
 Values
diff --git a/config.c b/config.c
index 3cfeb3d8bd..e0611fc342 100644
--- a/config.c
+++ b/config.c
@@ -317,6 +317,20 @@ static int include_by_branch(const char *cond, size_t cond_len)
 	return ret;
 }
 
+static int include_by_hostname(const char *cond, size_t cond_len)
+{
+	int ret;
+	char my_host[HOST_NAME_MAX + 1];
+	struct strbuf pattern = STRBUF_INIT;
+	if (xgethostname(my_host, sizeof(my_host)))
+		return 0;
+
+	strbuf_add(&pattern, cond, cond_len);
+	ret = !wildmatch(pattern.buf, my_host, 0);
+	strbuf_release(&pattern);
+	return ret;
+}
+
 static int add_remote_url(const char *var, const char *value,
 			  const struct config_context *ctx UNUSED, void *data)
 {
@@ -406,6 +420,8 @@ static int include_condition_is_true(const struct key_value_info *kvi,
 	else if (skip_prefix_mem(cond, cond_len, "hasconfig:remote.*.url:", &cond,
 				   &cond_len))
 		return include_by_remote_url(inc, cond, cond_len);
+	else if (skip_prefix_mem(cond, cond_len, "hostname:", &cond, &cond_len))
+		return include_by_hostname(cond, cond_len);
 
 	/* unknown conditionals are always false */
 	return 0;
diff --git a/t/t1305-config-include.sh b/t/t1305-config-include.sh
index 5cde79ef8c..ee78d9cade 100755
--- a/t/t1305-config-include.sh
+++ b/t/t1305-config-include.sh
@@ -357,4 +357,26 @@ test_expect_success 'include cycles are detected' '
 	grep "exceeded maximum include depth" stderr
 '
 
+test_expect_success 'conditional include, hostname' '
+	echo "[includeIf \"hostname:$(hostname)a\"]path=bar12" >>.git/config &&
+	echo "[test]twelve=12" >.git/bar12 &&
+	test_must_fail git config test.twelve &&
+
+	echo "[includeIf \"hostname:$(hostname)\"]path=bar12" >>.git/config &&
+	echo 12 >expect &&
+	git config test.twelve >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'conditional include, hostname, wildcard' '
+	echo "[includeIf \"hostname:$(hostname)a*\"]path=bar13" >>.git/config &&
+	echo "[test]thirteen=13" >.git/bar13 &&
+	test_must_fail git config test.thirteen &&
+
+	echo "[includeIf \"hostname:$(hostname)*\"]path=bar13" >>.git/config &&
+	echo 13 >expect &&
+	git config test.thirteen >actual &&
+	test_cmp expect actual
+'
+
 test_done
-- 
2.44.0