lib/git: add Git type with method IsIgnored

The Git type is for working with single git repository.

The [Git.IsIgnored] method is to check if the `path` is ignored by
git.
This is processed by matching it with all of the pattern in the
".gitignore" file from the path directory and its parent until the
root of Git repository.

1 files changed, 68 insertions, 2 deletions

diff --git a/lib/git/git.go b/lib/git/git.go
index 71240221..02877281 100644
--- a/lib/git/git.go
+++ b/lib/git/git.go
@@ -1,6 +1,5 @@
-// SPDX-FileCopyrightText: 2018 M. Shulhan <ms@kilabit.info>
-//
 // SPDX-License-Identifier: BSD-3-Clause
+// SPDX-FileCopyrightText: 2018 M. Shulhan <ms@kilabit.info>
 
 // Package git provide a wrapper for git command line interface.
 package git
@@ -13,6 +12,7 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"strings"
 
 	"git.sr.ht/~shulhan/pakakeh.go/lib/ini"
 )
@@ -28,6 +28,39 @@ var (
 	_stderr io.Writer = os.Stderr
 )
 
+// Git is a type for working with single git repository.
+type Git struct {
+	listIgnore map[string]*Gitignore
+
+	// absDir define the absolute path to the repository.
+	absDir string
+}
+
+// New start working on repository in directory `dir`.
+// If the `dir` does not contains ".git" directory it will return an error,
+// even if the parent directory may contains the ".git" directory.
+func New(dir string) (git *Git, err error) {
+	var logp = `New`
+	var fi os.FileInfo
+	var pathDotGit = filepath.Join(dir, `.git`)
+	fi, err = os.Stat(pathDotGit)
+	if err != nil {
+		return nil, fmt.Errorf(`%s: %q is not a git repository`, logp, dir)
+	}
+	if !fi.IsDir() {
+		return nil, fmt.Errorf(`%s: %q is not a git repository`, logp, dir)
+	}
+	dir, err = filepath.Abs(dir)
+	if err != nil {
+		return nil, fmt.Errorf(`%s: %w`, logp, err)
+	}
+	git = &Git{
+		absDir:     dir,
+		listIgnore: map[string]*Gitignore{},
+	}
+	return git, nil
+}
+
 // CheckoutRevision will set the HEAD to specific revision on specific branch.
 // Any untracked files and directories will be removed before checking out
 // existing branch or creating new branch.
@@ -188,6 +221,39 @@ func GetTag(repoDir, revision string) (tag string, err error) {
 	return tag, nil
 }
 
+// IsIgnored return true if the `path` is ignored by git.
+// This is processed by matching it with all of the patterns in the
+// ".gitignore" file inside the path directory and its parent, until the root
+// of Git repository.
+func (git *Git) IsIgnored(path string) (b bool) {
+	path = strings.TrimSpace(path)
+	if path == `` {
+		return true
+	}
+	// Traverse each directory from bottom to the top of git directory to
+	// load ".gitignore" file and match it with path.
+	var absPath = filepath.Join(git.absDir, path)
+	var dirGitignore = filepath.Dir(absPath)
+	var name = strings.TrimPrefix(absPath, dirGitignore)
+	name = strings.TrimLeft(name, `/`)
+	for strings.HasPrefix(dirGitignore, git.absDir) {
+		var ign *Gitignore
+		var ok bool
+		ign, ok = git.listIgnore[dirGitignore]
+		if !ok {
+			ign, _ = LoadGitignore(dirGitignore)
+			git.listIgnore[dirGitignore] = ign
+		}
+		if ign != nil && ign.IsIgnored(name) {
+			return true
+		}
+		dirGitignore = filepath.Dir(dirGitignore)
+		name = strings.TrimPrefix(absPath, dirGitignore)
+		name = strings.TrimLeft(name, `/`)
+	}
+	return false
+}
+
 // 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) {