[PATCH 1/2] Add support for a shared config file

["Nathan W. Panike" <nathan.panike@gmail.com>]

The idea is that a project develops indigenous aliases that
should be shared project-wide.  The only way to communicate this
now is by channels outside of git--email or IRC or such. We add
support for the case where a project configuration can be in
.gitconfig in the top level of the repository.

Signed-off-by: Nathan W. Panike <nathan.panike@gmail.com>
---
 builtin/config.c |    9 ++++++++-
 config.c         |   49 ++++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 56 insertions(+), 2 deletions(-)

diff --git a/builtin/config.c b/builtin/config.c
index ca4a0db..26c679d 100644
--- a/builtin/config.c
+++ b/builtin/config.c
@@ -154,7 +154,7 @@ static int get_value(const char *key_, const char *regex_)
 {
 	int ret = -1;
 	char *tl;
-	char *global = NULL, *repo_config = NULL;
+	char *global = NULL, *repo_config = NULL, *shared = NULL;
 	const char *system_wide = NULL, *local;
 
 	local = config_exclusive_filename;
@@ -165,6 +165,8 @@ static int get_value(const char *key_, const char *regex_)
 			global = xstrdup(mkpath("%s/.gitconfig", home));
 		if (git_config_system())
 			system_wide = git_etc_gitconfig();
+		if(git_config_shared())
+			shared=xstrdup(".gitconfig");
 	}
 
 	key = xstrdup(key_);
@@ -198,11 +200,15 @@ static int get_value(const char *key_, const char *regex_)
 		git_config_from_file(show_config, system_wide, NULL);
 	if (do_all && global)
 		git_config_from_file(show_config, global, NULL);
+	if (do_all && shared) 
+		git_config_from_shared_file(show_config, shared, NULL);	
 	if (do_all)
 		git_config_from_file(show_config, local, NULL);
 	git_config_from_parameters(show_config, NULL);
 	if (!do_all && !seen)
 		git_config_from_file(show_config, local, NULL);
+	if (!do_all && !seen && shared) 
+		git_config_from_shared_file(show_config, shared, NULL);	
 	if (!do_all && !seen && global)
 		git_config_from_file(show_config, global, NULL);
 	if (!do_all && !seen && system_wide)
@@ -222,6 +228,7 @@ static int get_value(const char *key_, const char *regex_)
 free_strings:
 	free(repo_config);
 	free(global);
+	free(shared);
 	return ret;
 }
 
diff --git a/config.c b/config.c
index c63d683..a9e6bec 100644
--- a/config.c
+++ b/config.c
@@ -795,6 +795,38 @@ int git_config_from_file(config_fn_t fn, const char *filename, void *data)
 	return ret;
 }
 
+struct config_interceptor {
+	config_fn_t fn;
+	void* data;
+};
+
+/*
+ * The purpose of this function is to keep a malicious contributor from
+ * poisoning our configuration.  The idea of a shared configuration it to
+ * pass around helpful stuff like aliases, but we do not want to allow someone
+ * to say, change our email address or the url of the remote.
+ */
+
+static int config_interceptor_fn(const char*name, const char* value, void* data)
+{
+	int ret=0;
+	struct config_interceptor *ci = (struct config_interceptor*)data;
+	if( !ci ) {
+		return -1;
+	}
+	if(!prefixcmp(name,"alias."))
+		ret = (*ci->fn)(name,value,ci->data);
+	return ret;
+}
+
+int git_config_from_shared_file(config_fn_t fn,const char* filename, void* data)
+{
+	struct config_interceptor ci;
+	ci.fn=fn;
+	ci.data=data;	
+	return git_config_from_file(config_interceptor_fn,filename,&ci);
+}
+
 const char *git_etc_gitconfig(void)
 {
 	static const char *system_wide;
@@ -819,6 +851,11 @@ int git_config_global(void)
 	return !git_env_bool("GIT_CONFIG_NOGLOBAL", 0);
 }
 
+int git_config_shared(void)
+{
+	return !git_env_bool("GIT_CONFIG_NOSHARED", 0);
+}
+
 int git_config_from_parameters(config_fn_t fn, void *data)
 {
 	static int loaded_environment;
@@ -840,7 +877,8 @@ int git_config(config_fn_t fn, void *data)
 	int ret = 0, found = 0;
 	char *repo_config = NULL;
 	const char *home = NULL;
-
+	const char * shared = NULL;
+	
 	/* Setting $GIT_CONFIG makes git read _only_ the given config file. */
 	if (config_exclusive_filename)
 		return git_config_from_file(fn, config_exclusive_filename, data);
@@ -860,6 +898,15 @@ int git_config(config_fn_t fn, void *data)
 		free(user_config);
 	}
 
+	if (git_config_shared()) {
+		char *shared_config=xstrdup(".gitconfig");
+		if (!access(shared_config, R_OK)) {
+			ret += git_config_from_shared_file(fn, shared_config, data);
+			found += 1;
+		}
+		free(shared_config);
+	}
+	
 	repo_config = git_pathdup("config");
 	if (!access(repo_config, R_OK)) {
 		ret += git_config_from_file(fn, repo_config, data);
-- 
1.7.3.2.347.gd33a62