Merge branch 'nd/conditional-config-include'

The configuration file learned a new "includeIf.<condition>.path"
that includes the contents of the given path only when the
condition holds.  This allows you to say "include this work-related
bit only in the repositories under my ~/work/ directory".

* nd/conditional-config-include:
  config: add conditional include
  config.txt: reflow the second include.path paragraph
  config.txt: clarify multiple key values in include.path

3 files changed, 218 insertions, 8 deletions

diff --git a/Documentation/config.txt b/Documentation/config.txt
index eccc012672..cf281f64f1 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -79,18 +79,69 @@ escape sequences) are invalid.
 Includes
 ~~~~~~~~
 
-You can include one config file from another by setting the special
+You can include a config file from another by setting the special
 `include.path` variable to the name of the file to be included. The
 variable takes a pathname as its value, and is subject to tilde
-expansion.
+expansion. `include.path` can be given multiple times.
 
-The
-included file is expanded immediately, as if its contents had been
+The included file is expanded immediately, as if its contents had been
 found at the location of the include directive. If the value of the
-`include.path` variable is a relative path, the path is considered to be
-relative to the configuration file in which the include directive was
-found.  See below for examples.
+`include.path` variable is a relative path, the path is considered to
+be relative to the configuration file in which the include directive
+was found.  See below for examples.
 
+Conditional includes
+~~~~~~~~~~~~~~~~~~~~
+
+You can include a config file from another conditionally by setting a
+`includeIf.<condition>.path` variable to the name of the file to be
+included. The variable's value is treated the same way as
+`include.path`. `includeIf.<condition>.path` can be given multiple times.
+
+The condition starts with a keyword followed by a colon and some data
+whose format and meaning depends on the keyword. Supported keywords
+are:
+
+`gitdir`::
+
+	The data that follows the keyword `gitdir:` is used as a glob
+	pattern. If the location of the .git directory matches the
+	pattern, the include condition is met.
++
+The .git location may be auto-discovered, or come from `$GIT_DIR`
+environment variable. If the repository is auto discovered via a .git
+file (e.g. from submodules, or a linked worktree), the .git location
+would be the final location where the .git directory is, not where the
+.git file is.
++
+The pattern can contain standard globbing wildcards and two additional
+ones, `**/` and `/**`, that can match multiple path components. Please
+refer to linkgit:gitignore[5] for details. For convenience:
+
+ * If the pattern starts with `~/`, `~` will be substituted with the
+   content of the environment variable `HOME`.
+
+ * If the pattern starts with `./`, it is replaced with the directory
+   containing the current config file.
+
+ * If the pattern does not start with either `~/`, `./` or `/`, `**/`
+   will be automatically prepended. For example, the pattern `foo/bar`
+   becomes `**/foo/bar` and would match `/any/path/to/foo/bar`.
+
+ * If the pattern ends with `/`, `**` will be automatically added. For
+   example, the pattern `foo/` becomes `foo/**`. In other words, it
+   matches "foo" and everything inside, recursively.
+
+`gitdir/i`::
+	This is the same as `gitdir` except that matching is done
+	case-insensitively (e.g. on case-insensitive file sytems)
+
+A few more notes on matching via `gitdir` and `gitdir/i`:
+
+ * Symlinks in `$GIT_DIR` are not resolved before matching.
+
+ * Note that "../" is not special and will match literally, which is
+   unlikely what you want.
 
 Example
 ~~~~~~~
@@ -119,6 +170,17 @@ Example
 		path = foo ; expand "foo" relative to the current file
 		path = ~/foo ; expand "foo" in your `$HOME` directory
 
+	; include if $GIT_DIR is /path/to/foo/.git
+	[includeIf "gitdir:/path/to/foo/.git"]
+		path = /path/to/foo.inc
+
+	; include for all repositories inside /path/to/group
+	[includeIf "gitdir:/path/to/group/"]
+		path = /path/to/foo.inc
+
+	; include for all repositories inside $HOME/to/group
+	[includeIf "gitdir:~/to/group/"]
+		path = /path/to/foo.inc
 
 Values
 ~~~~~~
diff --git a/config.c b/config.c
index eb7e310a11..1a4d85537b 100644
--- a/config.c
+++ b/config.c
@@ -13,6 +13,7 @@
 #include "hashmap.h"
 #include "string-list.h"
 #include "utf8.h"
+#include "dir.h"
 
 struct config_source {
 	struct config_source *prev;
@@ -170,9 +171,94 @@ static int handle_path_include(const char *path, struct config_include_data *inc
 	return ret;
 }
 
+static int prepare_include_condition_pattern(struct strbuf *pat)
+{
+	struct strbuf path = STRBUF_INIT;
+	char *expanded;
+	int prefix = 0;
+
+	expanded = expand_user_path(pat->buf);
+	if (expanded) {
+		strbuf_reset(pat);
+		strbuf_addstr(pat, expanded);
+		free(expanded);
+	}
+
+	if (pat->buf[0] == '.' && is_dir_sep(pat->buf[1])) {
+		const char *slash;
+
+		if (!cf || !cf->path)
+			return error(_("relative config include "
+				       "conditionals must come from files"));
+
+		strbuf_add_absolute_path(&path, cf->path);
+		slash = find_last_dir_sep(path.buf);
+		if (!slash)
+			die("BUG: how is this possible?");
+		strbuf_splice(pat, 0, 1, path.buf, slash - path.buf);
+		prefix = slash - path.buf + 1 /* slash */;
+	} else if (!is_absolute_path(pat->buf))
+		strbuf_insert(pat, 0, "**/", 3);
+
+	if (pat->len && is_dir_sep(pat->buf[pat->len - 1]))
+		strbuf_addstr(pat, "**");
+
+	strbuf_release(&path);
+	return prefix;
+}
+
+static int include_by_gitdir(const char *cond, size_t cond_len, int icase)
+{
+	struct strbuf text = STRBUF_INIT;
+	struct strbuf pattern = STRBUF_INIT;
+	int ret = 0, prefix;
+
+	strbuf_add_absolute_path(&text, get_git_dir());
+	strbuf_add(&pattern, cond, cond_len);
+	prefix = prepare_include_condition_pattern(&pattern);
+
+	if (prefix < 0)
+		goto done;
+
+	if (prefix > 0) {
+		/*
+		 * perform literal matching on the prefix part so that
+		 * any wildcard character in it can't create side effects.
+		 */
+		if (text.len < prefix)
+			goto done;
+		if (!icase && strncmp(pattern.buf, text.buf, prefix))
+			goto done;
+		if (icase && strncasecmp(pattern.buf, text.buf, prefix))
+			goto done;
+	}
+
+	ret = !wildmatch(pattern.buf + prefix, text.buf + prefix,
+			 icase ? WM_CASEFOLD : 0, NULL);
+
+done:
+	strbuf_release(&pattern);
+	strbuf_release(&text);
+	return ret;
+}
+
+static int include_condition_is_true(const char *cond, size_t cond_len)
+{
+
+	if (skip_prefix_mem(cond, cond_len, "gitdir:", &cond, &cond_len))
+		return include_by_gitdir(cond, cond_len, 0);
+	else if (skip_prefix_mem(cond, cond_len, "gitdir/i:", &cond, &cond_len))
+		return include_by_gitdir(cond, cond_len, 1);
+
+	/* unknown conditionals are always false */
+	return 0;
+}
+
 int git_config_include(const char *var, const char *value, void *data)
 {
 	struct config_include_data *inc = data;
+	const char *cond, *key;
+	int cond_len;
 	int ret;
 
 	/*
@@ -185,6 +271,12 @@ int git_config_include(const char *var, const char *value, void *data)
 
 	if (!strcmp(var, "include.path"))
 		ret = handle_path_include(value, inc);
+
+	if (!parse_config_key(var, "includeif", &cond, &cond_len, &key) &&
+	    (cond && include_condition_is_true(cond, cond_len)) &&
+	    !strcmp(key, "path"))
+		ret = handle_path_include(value, inc);
+
 	return ret;
 }
 
diff --git a/t/t1305-config-include.sh b/t/t1305-config-include.sh
index 9ba2ba11c3..e833939320 100755
--- a/t/t1305-config-include.sh
+++ b/t/t1305-config-include.sh
@@ -102,7 +102,7 @@ test_expect_success 'config modification does not affect includes' '
 
 test_expect_success 'missing include files are ignored' '
 	cat >.gitconfig <<-\EOF &&
-	[include]path = foo
+	[include]path = non-existent
 	[test]value = yes
 	EOF
 	echo yes >expect &&
@@ -152,6 +152,62 @@ test_expect_success 'relative includes from stdin line fail' '
 	test_must_fail git config --file - test.one
 '
 
+test_expect_success 'conditional include, both unanchored' '
+	git init foo &&
+	(
+		cd foo &&
+		echo "[includeIf \"gitdir:foo/\"]path=bar" >>.git/config &&
+		echo "[test]one=1" >.git/bar &&
+		echo 1 >expect &&
+		git config test.one >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'conditional include, $HOME expansion' '
+	(
+		cd foo &&
+		echo "[includeIf \"gitdir:~/foo/\"]path=bar2" >>.git/config &&
+		echo "[test]two=2" >.git/bar2 &&
+		echo 2 >expect &&
+		git config test.two >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'conditional include, full pattern' '
+	(
+		cd foo &&
+		echo "[includeIf \"gitdir:**/foo/**\"]path=bar3" >>.git/config &&
+		echo "[test]three=3" >.git/bar3 &&
+		echo 3 >expect &&
+		git config test.three >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'conditional include, relative path' '
+	echo "[includeIf \"gitdir:./foo/.git\"]path=bar4" >>.gitconfig &&
+	echo "[test]four=4" >bar4 &&
+	(
+		cd foo &&
+		echo 4 >expect &&
+		git config test.four >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'conditional include, both unanchored, icase' '
+	(
+		cd foo &&
+		echo "[includeIf \"gitdir/i:FOO/\"]path=bar5" >>.git/config &&
+		echo "[test]five=5" >.git/bar5 &&
+		echo 5 >expect &&
+		git config test.five >actual &&
+		test_cmp expect actual
+	)
+'
+
 test_expect_success 'include cycles are detected' '
 	cat >.gitconfig <<-\EOF &&
 	[test]value = gitconfig