add support for .git as file, fixes #348

2 files changed, 142 insertions, 9 deletions

diff --git a/repository.go b/repository.go
index bb59afe..8a7b348 100644
--- a/repository.go
+++ b/repository.go
@@ -3,8 +3,10 @@ package git
 import (
 	"errors"
 	"fmt"
+	stdioutil "io/ioutil"
 	"os"
 	"path/filepath"
+	"strings"
 
 	"gopkg.in/src-d/go-git.v4/config"
 	"gopkg.in/src-d/go-git.v4/internal/revision"
@@ -13,6 +15,7 @@ import (
 	"gopkg.in/src-d/go-git.v4/plumbing/storer"
 	"gopkg.in/src-d/go-git.v4/storage"
 	"gopkg.in/src-d/go-git.v4/storage/filesystem"
+	"gopkg.in/src-d/go-git.v4/utils/ioutil"
 
 	"gopkg.in/src-d/go-billy.v2"
 	"gopkg.in/src-d/go-billy.v2/osfs"
@@ -193,26 +196,69 @@ func PlainInit(path string, isBare bool) (*Repository, error) {
 // repository is bare or a normal one. If the path doesn't contain a valid
 // repository ErrRepositoryNotExists is returned
 func PlainOpen(path string) (*Repository, error) {
-	var wt, dot billy.Filesystem
+	dot, wt, err := dotGitToFilesystems(path)
+	if err != nil {
+		return nil, err
+	}
+
+	s, err := filesystem.NewStorage(dot)
+	if err != nil {
+		return nil, err
+	}
 
+	return Open(s, wt)
+}
+
+func dotGitToFilesystems(path string) (dot, wt billy.Filesystem, err error) {
 	fs := osfs.New(path)
-	if _, err := fs.Stat(".git"); err != nil {
+	fi, err := fs.Stat(".git")
+	if err != nil {
 		if !os.IsNotExist(err) {
-			return nil, err
+			return nil, nil, err
 		}
 
-		dot = fs
-	} else {
-		wt = fs
-		dot = fs.Dir(".git")
+		return fs, nil, nil
 	}
 
-	s, err := filesystem.NewStorage(dot)
+	if fi.IsDir() {
+		return fs.Dir(".git"), fs, nil
+	}
+
+	dot, err = dotGitFileToFilesystem(fs)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	return dot, fs, nil
+}
+
+func dotGitFileToFilesystem(fs billy.Filesystem) (billy.Filesystem, error) {
+	var err error
+
+	f, err := fs.Open(".git")
 	if err != nil {
 		return nil, err
 	}
+	defer ioutil.CheckClose(f, &err)
 
-	return Open(s, wt)
+	b, err := stdioutil.ReadAll(f)
+	if err != nil {
+		return nil, err
+	}
+
+	line := string(b)
+	const prefix = "gitdir: "
+	if !strings.HasPrefix(line, prefix) {
+		return nil, fmt.Errorf(".git file has no %s prefix", prefix)
+	}
+
+	gitdir := line[len(prefix):]
+	gitdir = strings.TrimSpace(gitdir)
+	if filepath.IsAbs(gitdir) {
+		return osfs.New(gitdir), nil
+	}
+
+	return fs.Dir(gitdir), err
 }
 
 // PlainClone a repository into the path with the given options, isBare defines
diff --git a/repository_test.go b/repository_test.go
index 77bfde2..fd8d405 100644
--- a/repository_test.go
+++ b/repository_test.go
@@ -272,6 +272,93 @@ func (s *RepositorySuite) TestPlainOpenNotBare(c *C) {
 	c.Assert(r, IsNil)
 }
 
+func (s *RepositorySuite) testPlainOpenGitFile(c *C, f func(string, string) string) {
+	dir, err := ioutil.TempDir("", "plain-open")
+	c.Assert(err, IsNil)
+	defer os.RemoveAll(dir)
+
+	r, err := PlainInit(dir, true)
+	c.Assert(err, IsNil)
+	c.Assert(r, NotNil)
+
+	altDir, err := ioutil.TempDir("", "plain-open")
+	c.Assert(err, IsNil)
+	defer os.RemoveAll(altDir)
+
+	err = ioutil.WriteFile(filepath.Join(altDir, ".git"), []byte(f(dir, altDir)), 0644)
+	c.Assert(err, IsNil)
+
+	r, err = PlainOpen(altDir)
+	c.Assert(err, IsNil)
+	c.Assert(r, NotNil)
+}
+
+func (s *RepositorySuite) TestPlainOpenBareAbsoluteGitDirFile(c *C) {
+	s.testPlainOpenGitFile(c, func(dir, altDir string) string {
+		return fmt.Sprintf("gitdir: %s\n", dir)
+	})
+}
+
+func (s *RepositorySuite) TestPlainOpenBareAbsoluteGitDirFileNoEOL(c *C) {
+	s.testPlainOpenGitFile(c, func(dir, altDir string) string {
+		return fmt.Sprintf("gitdir: %s", dir)
+	})
+}
+
+func (s *RepositorySuite) TestPlainOpenBareRelativeGitDirFile(c *C) {
+	s.testPlainOpenGitFile(c, func(dir, altDir string) string {
+		dir, err := filepath.Rel(altDir, dir)
+		c.Assert(err, IsNil)
+		return fmt.Sprintf("gitdir: %s\n", dir)
+	})
+}
+
+func (s *RepositorySuite) TestPlainOpenBareRelativeGitDirFileNoEOL(c *C) {
+	s.testPlainOpenGitFile(c, func(dir, altDir string) string {
+		dir, err := filepath.Rel(altDir, dir)
+		c.Assert(err, IsNil)
+		return fmt.Sprintf("gitdir: %s\n", dir)
+	})
+}
+
+func (s *RepositorySuite) TestPlainOpenBareRelativeGitDirFileTrailingGarbage(c *C) {
+	dir, err := ioutil.TempDir("", "plain-open")
+	c.Assert(err, IsNil)
+	defer os.RemoveAll(dir)
+
+	r, err := PlainInit(dir, true)
+	c.Assert(err, IsNil)
+	c.Assert(r, NotNil)
+
+	altDir, err := ioutil.TempDir("", "plain-open")
+	c.Assert(err, IsNil)
+	err = ioutil.WriteFile(filepath.Join(altDir, ".git"), []byte(fmt.Sprintf("gitdir: %s\nTRAILING", dir)), 0644)
+	c.Assert(err, IsNil)
+
+	r, err = PlainOpen(altDir)
+	c.Assert(err, Equals, ErrRepositoryNotExists)
+	c.Assert(r, IsNil)
+}
+
+func (s *RepositorySuite) TestPlainOpenBareRelativeGitDirFileBadPrefix(c *C) {
+	dir, err := ioutil.TempDir("", "plain-open")
+	c.Assert(err, IsNil)
+	defer os.RemoveAll(dir)
+
+	r, err := PlainInit(dir, true)
+	c.Assert(err, IsNil)
+	c.Assert(r, NotNil)
+
+	altDir, err := ioutil.TempDir("", "plain-open")
+	c.Assert(err, IsNil)
+	err = ioutil.WriteFile(filepath.Join(altDir, ".git"), []byte(fmt.Sprintf("xgitdir: %s\n", dir)), 0644)
+	c.Assert(err, IsNil)
+
+	r, err = PlainOpen(altDir)
+	c.Assert(err, ErrorMatches, ".*gitdir.*")
+	c.Assert(r, IsNil)
+}
+
 func (s *RepositorySuite) TestPlainOpenNotExists(c *C) {
 	r, err := PlainOpen("/not-exists/")
 	c.Assert(err, Equals, ErrRepositoryNotExists)