[PATCH] Do not load user or system gitconfig and gitattributes

[Jason at zx2c4.com (Jason A. Donenfeld)]

From: "Jason A. Donenfeld" <Jason at zx2c4.com>

While doing any kind of git loading, unset HOME variables and set
NOSYSTEM variables so that cgit does not load any settings that a user
may have set for his own /usr/bin/git usage.

This fixes a fatal error introduced with git 1.8, whereupon git would
fatally exit when failing to access particular files.

Reported-by: Ferry Huberts <ferry.huberts at pelagic.nl>
Tested-by: Jason A. Donenfeld <Jason at zx2c4.com>
Tested-by: Ferry Huberts <ferry.huberts at pelagic.nl>
Signed-off-by: Jason A. Donenfeld <Jason at zx2c4.com>
---
 cgit.c      | 24 ++++++++++++++++++++++++
 ui-commit.c |  1 -
 ui-log.c    |  1 -
 3 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/cgit.c b/cgit.c
index f73c7b0..0bf8972 100644
--- a/cgit.c
+++ b/cgit.c
@@ -459,12 +459,36 @@ static char *guess_defbranch(void)
 
 static int prepare_repo_cmd(struct cgit_context *ctx)
 {
+	char *user_home;
+	char *xdg_home;
 	unsigned char sha1[20];
 	int nongit = 0;
 	int rc;
 
+	/* The path to the git repository. */
 	setenv("GIT_DIR", ctx->repo->path, 1);
+
+	/* Do not look in /etc/ for gitconfig and gitattributes. */
+	setenv("GIT_CONFIG_NOSYSTEM", "1", 1);
+	setenv("GIT_ATTR_NOSYSTEM", "1", 1);
+
+	/* We unset HOME and XDG_CONFIG_HOME before calling the git setup function
+	 * so that we don't make unneccessary filesystem accesses. */
+	user_home = getenv("HOME");
+	xdg_home = getenv("XDG_CONFIG_HOME");
+	unsetenv("HOME");
+	unsetenv("XDG_CONFIG_HOME");
+
+	/* Setup the git directory and initialize the notes system. Both of these
+	 * load local configuration from the git repository, so we do them both while
+	 * the HOME variables are unset. */
 	setup_git_directory_gently(&nongit);
+	init_display_notes(NULL);
+
+	/* We restore the unset variables afterward. */
+	setenv("HOME", user_home, 1);
+	setenv("XDG_CONFIG_HOME", xdg_home, 1);
+
 	if (nongit) {
 		const char *name = ctx->repo->name;
 		rc = errno;
diff --git a/ui-commit.c b/ui-commit.c
index 6b41017..a5a6ea8 100644
--- a/ui-commit.c
+++ b/ui-commit.c
@@ -37,7 +37,6 @@ void cgit_print_commit(char *hex, const char *prefix)
 	}
 	info = cgit_parse_commit(commit);
 
-	init_display_notes(NULL);
 	format_display_notes(sha1, &notes, PAGE_ENCODING, 0);
 
 	load_ref_decorations(DECORATE_FULL_REFS);
diff --git a/ui-log.c b/ui-log.c
index 93af0ce..2aa12c3 100644
--- a/ui-log.c
+++ b/ui-log.c
@@ -403,7 +403,6 @@ void cgit_print_log(const char *tip, int ofs, int cnt, char *grep, char *pattern
 		commit->parents = NULL;
 	}
 
-	init_display_notes(NULL);
 	for (i = 0; i < cnt && (commit = get_revision(&rev)) != NULL; i++) {
 		print_commit(commit, &rev);
 		free(commit->buffer);
-- 
1.8.1.5