1 files changed, 43 insertions, 0 deletions
diff --git a/storage/filesystem/dotgit/dotgit_setref.go b/storage/filesystem/dotgit/dotgit_setref.go
new file mode 100644
index 0000000..d27c1a3
--- /dev/null
+++ b/storage/filesystem/dotgit/dotgit_setref.go
@@ -0,0 +1,43 @@
+// +build !norwfs
+
+package dotgit
+
+import (
+	"os"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/utils/ioutil"
+)
+
+func (d *DotGit) setRef(fileName, content string, old *plumbing.Reference) (err error) {
+	// If we are not checking an old ref, just truncate the file.
+	mode := os.O_RDWR | os.O_CREATE
+	if old == nil {
+		mode |= os.O_TRUNC
+	}
+
+	f, err := d.fs.OpenFile(fileName, mode, 0666)
+	if err != nil {
+		return err
+	}
+
+	defer ioutil.CheckClose(f, &err)
+
+	// Lock is unlocked by the deferred Close above. This is because Unlock
+	// does not imply a fsync and thus there would be a race between
+	// Unlock+Close and other concurrent writers. Adding Sync to go-billy
+	// could work, but this is better (and avoids superfluous syncs).
+	err = f.Lock()
+	if err != nil {
+		return err
+	}
+
+	// this is a no-op to call even when old is nil.
+	err = d.checkReferenceAndTruncate(f, old)
+	if err != nil {
+		return err
+	}
+
+	_, err = f.Write([]byte(content))
+	return err
+}