1 files changed, 80 insertions, 0 deletions
diff --git a/git-access.c b/git-access.c
new file mode 100644
index 000000000..3b01623b9
--- /dev/null
+++ b/git-access.c
@@ -0,0 +1,80 @@
+#include <stdio.h>
+#include <ctype.h>
+#include <string.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <time.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <git2.h>
+
+#include "dive.h"
+
+/*
+ * If it's not a git repo, return NULL. Be very conservative.
+ */
+struct git_repository *is_git_repository(const char *filename, const char **branchp)
+{
+	int flen, blen, ret;
+	struct stat st;
+	git_repository *repo;
+	char *loc, *branch;
+
+	flen = strlen(filename);
+	if (!flen || filename[--flen] != ']')
+		return NULL;
+
+	/* Find the matching '[' */
+	blen = 0;
+	while (flen && filename[--flen] != '[')
+		blen++;
+
+	if (!flen)
+		return NULL;
+
+	/*
+	 * This is the "point of no return": the name matches
+	 * the git repository name rules, and we will no longer
+	 * return NULL.
+	 *
+	 * We will either return "dummy_git_repository" and the
+	 * branch pointer will have the _whole_ filename in it,
+	 * or we will return a real git repository with the
+	 * branch pointer being filled in with just the branch
+	 * name.
+	 *
+	 * The actual git reading/writing routines can use this
+	 * to generate proper error messages.
+	 */
+	*branchp = filename;
+	loc = malloc(flen+1);
+	if (!loc)
+		return dummy_git_repository;
+	memcpy(loc, filename, flen);
+	loc[flen] = 0;
+
+	branch = malloc(blen+1);
+	if (!branch) {
+		free(loc);
+		return dummy_git_repository;
+	}
+	memcpy(branch, filename+flen+1, blen);
+	branch[blen] = 0;
+
+	if (stat(loc, &st) < 0 || !S_ISDIR(st.st_mode)) {
+		free(loc);
+		free(branch);
+		return dummy_git_repository;
+	}
+
+	ret = git_repository_open(&repo, loc);
+	free(loc);
+	if (ret < 0) {
+		free(branch);
+		return dummy_git_repository;
+	}
+	*branchp = branch;
+	return repo;
+}