Do not verify filenames in a bare repository

For example, it makes no sense to check the presence of a file
named "HEAD" when calling "git log HEAD" in a bare repository.

Noticed by Han-Wen Nienhuys.
Signed-off-by: NJohannes Schindelin <Johannes.Schindelin@gmx.de>

cache.h

@@ -129,6 +129,7 @@ extern int cache_errno;
 
 extern int is_bare_repository_cfg;
 extern int is_bare_repository(void);
+extern int is_inside_git_dir(void);
 extern const char *get_git_dir(void);
 extern char *get_object_directory(void);
 extern char *get_refs_directory(void);

setup.c

@@ -95,6 +95,8 @@ void verify_non_filename(const char *prefix, const char *arg)
 	const char *name;
 	struct stat st;
 
+	if (is_inside_git_dir())
+		return;
 	if (*arg == '-')
 		return; /* flag */
 	name = prefix ? prefix_filename(prefix, strlen(prefix), arg) : arg;
@@ -168,6 +170,28 @@ static int is_git_directory(const char *suspect)
 	return 1;
 }
 
+static int inside_git_dir = -1;
+
+int is_inside_git_dir(void)
+{
+	if (inside_git_dir < 0) {
+		char buffer[1024];
+
+		if (is_bare_repository())
+			return (inside_git_dir = 1);
+		if (getcwd(buffer, sizeof(buffer))) {
+			const char *git_dir = get_git_dir(), *cwd = buffer;
+			while (*git_dir && *git_dir == *cwd) {
+				git_dir++;
+				cwd++;
+			}
+			inside_git_dir = !*git_dir;
+		} else
+			inside_git_dir = 0;
+	}
+	return inside_git_dir;
+}
+
 const char *setup_git_directory_gently(int *nongit_ok)
 {
 	static char cwd[PATH_MAX+1];
@@ -206,6 +230,7 @@ const char *setup_git_directory_gently(int *nongit_ok)
 					if (chdir(cwd))
 						die("Cannot come back to cwd");
 					setenv(GIT_DIR_ENVIRONMENT, cwd, 1);
+					inside_git_dir = 1;
 					return NULL;
 				}
 				if (nongit_ok) {
@@ -226,6 +251,7 @@ const char *setup_git_directory_gently(int *nongit_ok)
 	offset++;
 	cwd[len++] = '/';
 	cwd[len] = 0;
+	inside_git_dir = !strncmp(cwd + offset, ".git/", 5);
 	return cwd + offset;
 }
 

t/t1020-subdirectory.sh

@@ -106,4 +106,33 @@ test_expect_success 'read-tree' '
 	cmp ../one ../original.one
 '
 
+test_expect_success 'no file/rev ambuguity check inside .git' '
+	cd $HERE &&
+	git commit -a -m 1 &&
+	cd $HERE/.git &&
+	git show -s HEAD
+'
+
+test_expect_success 'no file/rev ambuguity check inside a bare repo' '
+	cd $HERE &&
+	git clone -s --bare .git foo.git &&
+	cd foo.git && GIT_DIR=. git show -s HEAD
+'
+
+# This still does not work as it should...
+: test_expect_success 'no file/rev ambuguity check inside a bare repo' '
+	cd $HERE &&
+	git clone -s --bare .git foo.git &&
+	cd foo.git && git show -s HEAD
+'
+
+test_expect_success 'detection should not be fooled by a symlink' '
+	cd $HERE &&
+	rm -fr foo.git &&
+	git clone -s .git another &&
+	ln -s another yetanother &&
+	cd yetanother/.git &&
+	git show -s HEAD
+'
+
 test_done