Add partial submodules support

This adds support for retrieiving the commit, branch &c. for submodules.  It
does not compute the correct `root` information, but it's still an improvement
over v1.2.0 (which did not throw but provided no information) and v1.3.0 (which
threw).

[Fix #27]

Author: hjdivad

index.js

@@ -20,16 +20,32 @@ function findRepoHandleLinkedWorktree(gitPath) {
       commonGitDir: gitPath,
     };
   } else {
+    // We have a file that tells us where to find the worktree git dir.  Once we
+    // look there we'll know how to find the common git dir, depending on
+    // whether it's a linked worktree git dir, or a submodule dir
+
     var linkedGitDir = fs.readFileSync(gitPath).toString();
-    var worktreeGitDir = /gitdir: (.*)/.exec(linkedGitDir)[1];
+    var worktreeGitDirUnresolved = /gitdir: (.*)/.exec(linkedGitDir)[1];
+    var worktreeGitDir = path.resolve(worktreeGitDirUnresolved);
     var commonDirPath = path.join(worktreeGitDir, 'commondir');
-    var commonDirRelative = fs.readFileSync(commonDirPath).toString().replace(/\r?\n$/, '');
-    var commonDir = path.resolve(path.join(worktreeGitDir, commonDirRelative));
+    if (fs.existsSync(commonDirPath)) {
+      // this directory contains a `commondir` file; we're within a linked
+      // worktree
 
-    return {
-      worktreeGitDir: path.resolve(worktreeGitDir),
-      commonGitDir: commonDir,
-    };
+      var commonDirRelative = fs.readFileSync(commonDirPath).toString().replace(/\r?\n$/, '');
+      var commonDir = path.resolve(path.join(worktreeGitDir, commonDirRelative));
+
+      return {
+        worktreeGitDir: worktreeGitDir,
+        commonGitDir: commonDir,
+      };
+    } else {
+      // there is no `commondir` file; we're in a submodule
+      return {
+        worktreeGitDir: worktreeGitDir,
+        commonGitDir: worktreeGitDir,
+      };
+    }
   }
 }
 

tests/fixtures/submodule/dot-git/HEAD

@@ -0,0 +1 @@
+9dac893d5a83c02344d91e79dad8904889aeacb1

tests/fixtures/submodule/dot-git/modules/my-submodule/HEAD

@@ -0,0 +1 @@
+409372f3bd07c11bfacee3963f48571d675268d7

tests/fixtures/submodule/my-submodule/dot-git

@@ -0,0 +1 @@
+gitdir: ../dot-git/modules/my-submodule

tests/index.js

@@ -84,6 +84,16 @@ describe('git-repo-info', function() {
         commonGitDir: path.join(testFixturesPath, 'linked-worktree', 'dot-git'),
       });
     });
+
+    it('finds a repo via a submodule', function() {
+      process.chdir(path.join(testFixturesPath, 'submodule', 'my-submodule'));
+
+      var foundPathInfo = repoInfo._findRepo();
+      assert.deepEqual(foundPathInfo, {
+        worktreeGitDir: path.join(testFixturesPath, 'submodule', 'dot-git', 'modules', 'my-submodule'),
+        commonGitDir: path.join(testFixturesPath, 'submodule', 'dot-git', 'modules', 'my-submodule'),
+      });
+    });
   });
 
   describe('repoInfo', function() {
@@ -290,6 +300,29 @@ describe('git-repo-info', function() {
 
       assert.deepEqual(result, expected);
     });
+
+    it('returns an object for repo info for submodules', function() {
+      process.chdir(path.join(testFixturesPath, 'submodule', 'my-submodule'));
+      var result = repoInfo();
+
+      var expected = {
+        branch: null,
+        sha: '409372f3bd07c11bfacee3963f48571d675268d7',
+        abbreviatedSha: '409372f3bd',
+        tag: null,
+        committer: null,
+        committerDate: null,
+        author: null,
+        authorDate: null,
+        commitMessage: null,
+        // This is a pretty meaningless "root" path.  The other information is
+        // correct, but we do not have full support for submodules at the
+        // moment.
+        root: path.join(testFixturesPath, 'submodule', 'dot-git', 'modules')
+      };
+
+      assert.deepEqual(result, expected);
+    });
   });
 
   describe('repoInfo().root', function() {