lib/git: add method LogFollow

The LogFollow method return history of single file `path`, following
rename.

This method accept second paramter "format", default to
'%h,%at,%an,%ae,%s' which print short hash, author commit timestamp,
author name, author email, and subject; respectively separated by comma.

3 files changed, 66 insertions, 0 deletions

diff --git a/CHANGELOG.adoc b/CHANGELOG.adoc
index 5d9c003d..2d640a1a 100644
--- a/CHANGELOG.adoc
+++ b/CHANGELOG.adoc
@@ -46,6 +46,15 @@ to the request, and the server will return immediately.
 Zero status code indicates that the function did not process the request,
 it is up to server to process the returned node `out`.
 
+**🌱 lib/git: add method LogFollow**
+
+The LogFollow method return history of single file `path`, following
+rename.
+
+This method accept second paramter "format", default to
+'%h,%at,%an,%ae,%s' which print short hash, author commit timestamp,
+author name, author email, and subject; respectively separated by comma.
+
 //}}}
 //{{{
 [#v0_60_2]
diff --git a/lib/git/git.go b/lib/git/git.go
index 43a27bf5..3ee5c376 100644
--- a/lib/git/git.go
+++ b/lib/git/git.go
@@ -272,6 +272,39 @@ func (git *Git) IsIgnored(path string) (b bool) {
 	return false
 }
 
+// LogFollow return history of single file `path`, following rename.
+//
+// The format parameter set the output format, default to '%h,%at,%an,%ae,%s'
+// which print short hash, author commit timestamp, author name, author email,
+// and subject; respectively separated by comma.
+func (git *Git) LogFollow(path, format string) (logs []string, err error) {
+	if format == `` {
+		format = `%h,%at,%an,%ae,%s`
+	}
+
+	var cmd *exec.Cmd
+	cmd = exec.Command(`git`)
+	cmd.Args = append(cmd.Args, `--no-pager`, `log`, `--follow`, `--format=`+format, path)
+	cmd.Dir = git.absDir
+	cmd.Stderr = _stderr
+
+	var stdout []byte
+	stdout, err = cmd.Output()
+	if err != nil {
+		return nil, fmt.Errorf(`LogFollow %s: %w`, path, err)
+	}
+
+	lines := bytes.Split(stdout, []byte{'\n'})
+	logs = make([]string, 0, len(lines))
+	for _, line := range lines {
+		if len(line) == 0 {
+			break
+		}
+		logs = append(logs, string(line))
+	}
+	return logs, nil
+}
+
 // LatestCommit get the latest commit hash in short format from "ref".
 // If ref is empty, its default to "origin/master".
 func LatestCommit(repoDir, ref string) (commit string, err error) {
diff --git a/lib/git/git_test.go b/lib/git/git_test.go
index 2ea5aba4..e4cb5a26 100644
--- a/lib/git/git_test.go
+++ b/lib/git/git_test.go
@@ -194,6 +194,30 @@ func TestGit_IsIgnored(t *testing.T) {
 	}
 }
 
+func TestGit_LogFollow(t *testing.T) {
+	agit, err := New(`../../`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	path := `lib/_hunspell/affix.go`
+	logs, err := agit.LogFollow(path, ``)
+	if err != nil {
+		t.Fatal(err)
+	}
+	exp := []string{
+		`144549f8,1737804887,Shulhan,ms@kilabit.info,lib/hunspell: rename the package to "_hunspell"`,
+		`66e6542e,1694357806,Shulhan,ms@kilabit.info,lib/hunspell: realign struct for better size allocation`,
+		`0c9abc1a,1652108042,Shulhan,ms@kilabit.info,all: reformat all codes using gofmt 1.19 (the Go tip)`,
+		`9ca9757d,1591803682,Shulhan,m.shulhan@gmail.com,all: update email address`,
+		`b0fa5a47,1585156612,Shulhan,m.shulhan@gmail.com,all: fix and suppress linter warnings`,
+		`33d58b98,1585151378,Shulhan,m.shulhan@gmail.com,hunspell: add field Parent to Stem`,
+		`367e15a8,1585139124,Shulhan,m.shulhan@gmail.com,hunspell: change the stem.apply parameter from string to *Stem`,
+		`099a24de,1579628651,Shulhan,m.shulhan@gmail.com,hunspell: split the affix options and dictionary into different types`,
+		`3d772dff,1572967023,Shulhan,m.shulhan@gmail.com,lib/hunspell: implementation of hunspell in pure Go`,
+	}
+	test.Assert(t, path, exp, logs)
+}
+
 func TestGetRemoteURL(t *testing.T) {
 	cases := []struct {
 		desc                 string