1 files changed, 252 insertions, 0 deletions
diff --git a/path.c b/path.c
new file mode 100644
index 0000000000..334b2bd195
--- /dev/null
+++ b/path.c
@@ -0,0 +1,252 @@
+/*
+ * I'm tired of doing "vsnprintf()" etc just to open a
+ * file, so here's a "return static buffer with printf"
+ * interface for paths.
+ *
+ * It's obviously not thread-safe. Sue me. But it's quite
+ * useful for doing things like
+ *
+ *   f = open(mkpath("%s/%s.git", base, name), O_RDONLY);
+ *
+ * which is what it's designed for.
+ */
+#include "cache.h"
+#include <pwd.h>
+
+static char pathname[PATH_MAX];
+static char bad_path[] = "/bad-path/";
+
+static char *cleanup_path(char *path)
+{
+	/* Clean it up */
+	if (!memcmp(path, "./", 2)) {
+		path += 2;
+		while (*path == '/')
+			path++;
+	}
+	return path;
+}
+
+char *mkpath(const char *fmt, ...)
+{
+	va_list args;
+	unsigned len;
+
+	va_start(args, fmt);
+	len = vsnprintf(pathname, PATH_MAX, fmt, args);
+	va_end(args);
+	if (len >= PATH_MAX)
+		return bad_path;
+	return cleanup_path(pathname);
+}
+
+char *git_path(const char *fmt, ...)
+{
+	const char *git_dir = get_git_dir();
+	va_list args;
+	unsigned len;
+
+	len = strlen(git_dir);
+	if (len > PATH_MAX-100)
+		return bad_path;
+	memcpy(pathname, git_dir, len);
+	if (len && git_dir[len-1] != '/')
+		pathname[len++] = '/';
+	va_start(args, fmt);
+	len += vsnprintf(pathname + len, PATH_MAX - len, fmt, args);
+	va_end(args);
+	if (len >= PATH_MAX)
+		return bad_path;
+	return cleanup_path(pathname);
+}
+
+
+/* git_mkstemp() - create tmp file honoring TMPDIR variable */
+int git_mkstemp(char *path, size_t len, const char *template)
+{
+	char *env, *pch = path;
+
+	if ((env = getenv("TMPDIR")) == NULL) {
+		strcpy(pch, "/tmp/");
+		len -= 5;
+		pch += 5;
+	} else {
+		size_t n = snprintf(pch, len, "%s/", env);
+
+		len -= n;
+		pch += n;
+	}
+
+	safe_strncpy(pch, template, len);
+
+	return mkstemp(path);
+}
+
+
+char *safe_strncpy(char *dest, const char *src, size_t n)
+{
+	strncpy(dest, src, n);
+	dest[n - 1] = '\0';
+
+	return dest;
+}
+
+int validate_symref(const char *path)
+{
+	struct stat st;
+	char *buf, buffer[256];
+	int len, fd;
+
+	if (lstat(path, &st) < 0)
+		return -1;
+
+	/* Make sure it is a "refs/.." symlink */
+	if (S_ISLNK(st.st_mode)) {
+		len = readlink(path, buffer, sizeof(buffer)-1);
+		if (len >= 5 && !memcmp("refs/", buffer, 5))
+			return 0;
+		return -1;
+	}
+
+	/*
+	 * Anything else, just open it and try to see if it is a symbolic ref.
+	 */
+	fd = open(path, O_RDONLY);
+	if (fd < 0)
+		return -1;
+	len = read(fd, buffer, sizeof(buffer)-1);
+	close(fd);
+
+	/*
+	 * Is it a symbolic ref?
+	 */
+	if (len < 4 || memcmp("ref:", buffer, 4))
+		return -1;
+	buf = buffer + 4;
+	len -= 4;
+	while (len && isspace(*buf))
+		buf++, len--;
+	if (len >= 5 && !memcmp("refs/", buf, 5))
+		return 0;
+	return -1;
+}
+
+static char *user_path(char *buf, char *path, int sz)
+{
+	struct passwd *pw;
+	char *slash;
+	int len, baselen;
+
+	if (!path || path[0] != '~')
+		return NULL;
+	path++;
+	slash = strchr(path, '/');
+	if (path[0] == '/' || !path[0]) {
+		pw = getpwuid(getuid());
+	}
+	else {
+		if (slash) {
+			*slash = 0;
+			pw = getpwnam(path);
+			*slash = '/';
+		}
+		else
+			pw = getpwnam(path);
+	}
+	if (!pw || !pw->pw_dir || sz <= strlen(pw->pw_dir))
+		return NULL;
+	baselen = strlen(pw->pw_dir);
+	memcpy(buf, pw->pw_dir, baselen);
+	while ((1 < baselen) && (buf[baselen-1] == '/')) {
+		buf[baselen-1] = 0;
+		baselen--;
+	}
+	if (slash && slash[1]) {
+		len = strlen(slash);
+		if (sz <= baselen + len)
+			return NULL;
+		memcpy(buf + baselen, slash, len + 1);
+	}
+	return buf;
+}
+
+/*
+ * First, one directory to try is determined by the following algorithm.
+ *
+ * (0) If "strict" is given, the path is used as given and no DWIM is
+ *     done. Otherwise:
+ * (1) "~/path" to mean path under the running user's home directory;
+ * (2) "~user/path" to mean path under named user's home directory;
+ * (3) "relative/path" to mean cwd relative directory; or
+ * (4) "/absolute/path" to mean absolute directory.
+ *
+ * Unless "strict" is given, we try access() for existence of "%s.git/.git",
+ * "%s/.git", "%s.git", "%s" in this order.  The first one that exists is
+ * what we try.
+ *
+ * Second, we try chdir() to that.  Upon failure, we return NULL.
+ *
+ * Then, we try if the current directory is a valid git repository.
+ * Upon failure, we return NULL.
+ *
+ * If all goes well, we return the directory we used to chdir() (but
+ * before ~user is expanded), avoiding getcwd() resolving symbolic
+ * links.  User relative paths are also returned as they are given,
+ * except DWIM suffixing.
+ */
+char *enter_repo(char *path, int strict)
+{
+	static char used_path[PATH_MAX];
+	static char validated_path[PATH_MAX];
+
+	if (!path)
+		return NULL;
+
+	if (!strict) {
+		static const char *suffix[] = {
+			".git/.git", "/.git", ".git", "", NULL,
+		};
+		int len = strlen(path);
+		int i;
+		while ((1 < len) && (path[len-1] == '/')) {
+			path[len-1] = 0;
+			len--;
+		}
+		if (PATH_MAX <= len)
+			return NULL;
+		if (path[0] == '~') {
+			if (!user_path(used_path, path, PATH_MAX))
+				return NULL;
+			strcpy(validated_path, path);
+			path = used_path;
+		}
+		else if (PATH_MAX - 10 < len)
+			return NULL;
+		else {
+			path = strcpy(used_path, path);
+			strcpy(validated_path, path);
+		}
+		len = strlen(path);
+		for (i = 0; suffix[i]; i++) {
+			strcpy(path + len, suffix[i]);
+			if (!access(path, F_OK)) {
+				strcat(validated_path, suffix[i]);
+				break;
+			}
+		}
+		if (!suffix[i] || chdir(path))
+			return NULL;
+		path = validated_path;
+	}
+	else if (chdir(path))
+		return NULL;
+
+	if (access("objects", X_OK) == 0 && access("refs", X_OK) == 0 &&
+	    validate_symref("HEAD") == 0) {
+		putenv("GIT_DIR=.");
+		check_repository_format();
+		return path;
+	}
+
+	return NULL;
+}