Merge branch 'js/fopen-harder' into maint

Some codepaths used fopen(3) when opening a fixed path in $GIT_DIR
(e.g. COMMIT_EDITMSG) that is meant to be left after the command is
done.  This however did not work well if the repository is set to
be shared with core.sharedRepository and the umask of the previous
user is tighter.  They have been made to work better by calling
unlink(2) and retrying after fopen(3) fails with EPERM.

* js/fopen-harder:
  Handle more file writes correctly in shared repos
  commit: allow editing the commit message even in shared repos

5 files changed, 17 insertions, 3 deletions

diff --git a/builtin/commit.c b/builtin/commit.c
index d054f84960..89bf6ad38a 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -761,7 +761,7 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
 		hook_arg2 = "";
 	}
 
-	s->fp = fopen(git_path(commit_editmsg), "w");
+	s->fp = fopen_for_writing(git_path(commit_editmsg));
 	if (s->fp == NULL)
 		die_errno(_("could not open '%s'"), git_path(commit_editmsg));
 
diff --git a/builtin/fast-export.c b/builtin/fast-export.c
index d9ac5d8410..2471297f71 100644
--- a/builtin/fast-export.c
+++ b/builtin/fast-export.c
@@ -880,7 +880,7 @@ static void export_marks(char *file)
 	FILE *f;
 	int e = 0;
 
-	f = fopen(file, "w");
+	f = fopen_for_writing(file);
 	if (!f)
 		die_errno("Unable to open marks file %s for writing.", file);
 
diff --git a/builtin/fetch.c b/builtin/fetch.c
index c85f3471d4..9e24bb485f 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -837,7 +837,7 @@ static void check_not_current_branch(struct ref *ref_map)
 static int truncate_fetch_head(void)
 {
 	const char *filename = git_path_fetch_head();
-	FILE *fp = fopen(filename, "w");
+	FILE *fp = fopen_for_writing(filename);
 
 	if (!fp)
 		return error(_("cannot open %s: %s\n"), filename, strerror(errno));
diff --git a/git-compat-util.h b/git-compat-util.h
index 2da0a75a38..e8f2867228 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -733,6 +733,7 @@ extern int xmkstemp_mode(char *template, int mode);
 extern int odb_mkstemp(char *template, size_t limit, const char *pattern);
 extern int odb_pack_keep(char *name, size_t namesz, const unsigned char *sha1);
 extern char *xgetcwd(void);
+extern FILE *fopen_for_writing(const char *path);
 
 #define REALLOC_ARRAY(x, alloc) (x) = xrealloc((x), (alloc) * sizeof(*(x)))
 
diff --git a/wrapper.c b/wrapper.c
index c95e2906b8..52001789de 100644
--- a/wrapper.c
+++ b/wrapper.c
@@ -375,6 +375,19 @@ FILE *xfdopen(int fd, const char *mode)
 	return stream;
 }
 
+FILE *fopen_for_writing(const char *path)
+{
+	FILE *ret = fopen(path, "w");
+
+	if (!ret && errno == EPERM) {
+		if (!unlink(path))
+			ret = fopen(path, "w");
+		else
+			errno = EPERM;
+	}
+	return ret;
+}
+
 int xmkstemp(char *template)
 {
 	int fd;