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package dotgit
import (
"fmt"
"os"
"gopkg.in/src-d/go-git.v4/plumbing"
"gopkg.in/src-d/go-git.v4/utils/ioutil"
"gopkg.in/src-d/go-billy.v4"
)
func (d *DotGit) setRef(fileName, content string, old *plumbing.Reference) (err error) {
if billy.CapabilityCheck(d.fs, billy.ReadAndWriteCapability) {
return d.setRefRwfs(fileName, content, old)
}
return d.setRefNorwfs(fileName, content, old)
}
func (d *DotGit) setRefRwfs(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
}
// There are some filesystems that don't support opening files in RDWD mode.
// In these filesystems the standard SetRef function can not be used as it
// reads the reference file to check that it's not modified before updating it.
//
// This version of the function writes the reference without extra checks
// making it compatible with these simple filesystems. This is usually not
// a problem as they should be accessed by only one process at a time.
func (d *DotGit) setRefNorwfs(fileName, content string, old *plumbing.Reference) error {
_, err := d.fs.Stat(fileName)
if err == nil && old != nil {
fRead, err := d.fs.Open(fileName)
if err != nil {
return err
}
ref, err := d.readReferenceFrom(fRead, old.Name().String())
fRead.Close()
if err != nil {
return err
}
if ref.Hash() != old.Hash() {
return fmt.Errorf("reference has changed concurrently")
}
}
f, err := d.fs.Create(fileName)
if err != nil {
return err
}
defer f.Close()
_, err = f.Write([]byte(content))
return err
}
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