Add Repository.relativize(path)

README.md

@@ -217,6 +217,15 @@ Returns `true` if the path is a submodule, false otherwise.
 Reread the index to update any values that have changed since the last time the
 index was read.
 
+### Repository.relativize(path)
+
+Relativize the given path to the repository's working directory.
+
+`path` - The string path to relativize.
+
+Returns a repository-relative path if the given path is prefixed with the
+repository's working directory path.
+
 ### Repository.release()
 
 Release the repository and close all file handles it has open.  No other methods

spec/git-spec.coffee

@@ -272,3 +272,16 @@ describe "git", ->
       expect(diffs[0].oldLines).toBe 1
       expect(diffs[0].newStart).toBe 0
       expect(diffs[0].newLines).toBe 0
+
+  describe '.relativize(path)', ->
+    it 'relativizes the given path to the working directory of the repository', ->
+      repo = git.open(__dirname)
+      workingDirectory = repo.getWorkingDirectory()
+
+      expect(repo.relativize(path.join(workingDirectory, 'a.txt'))).toBe 'a.txt'
+      expect(repo.relativize(path.join(workingDirectory, 'a/b/c.txt'))).toBe 'a/b/c.txt'
+      expect(repo.relativize('a.txt')).toBe 'a.txt'
+      expect(repo.relativize('/not/in/working/dir')).toBe '/not/in/working/dir'
+      expect(repo.relativize(null)).toBe null
+      expect(repo.relativize()).toBeUndefined()
+      expect(repo.relativize('')).toBe ''

src/git.coffee

@@ -76,6 +76,16 @@ Repository.prototype.getAheadBehindCount = ->
   counts.behind = @getCommitCount(upstreamCommit, mergeBase)
   counts
 
+Repository.prototype.relativize = (path) ->
+  return path unless path?
+  return path unless path[0] is '/'
+
+  workingDirectory = @getWorkingDirectory()
+  if workingDirectory and path.indexOf("#{workingDirectory}/") is 0
+    path.substring(workingDirectory.length + 1)
+  else
+    path
+
 exports.open = (path) ->
   repository = new Repository(path)
   if repository.exists()