From 59e7522fe36b370a6eaf54dfdc6751948befa1be Mon Sep 17 00:00:00 2001
From: Devon Blandin <dblandin@gmail.com>
Date: Mon, 6 Jun 2016 12:11:50 -0400
Subject: [PATCH] Use git hash-object for blob id if available

This commit updates file blob_id generation by first shelling out to `git
hash-object`. If `git` or the file is unavailable, we'll fallback to our `sha1`
computation.
---
 formatter.js |  2 +-
 git_info.js  | 31 ++++++++++++++++++++++++-------
 2 files changed, 25 insertions(+), 8 deletions(-)

diff --git a/formatter.js b/formatter.js
index 370464b..e95f5d3 100644
--- a/formatter.js
+++ b/formatter.js
@@ -94,7 +94,7 @@ Formatter.prototype.sourceFiles = function(data) {
 
     source_files.push({
       name: fileName,
-      blob_id: git.calculateBlobId(content),
+      blob_id: git.blobId(elem.file, content),
       coverage: JSON.stringify(coverage)
     });
   });
diff --git a/git_info.js b/git_info.js
index eb80c17..e34a8dc 100644
--- a/git_info.js
+++ b/git_info.js
@@ -1,6 +1,14 @@
 var crypto = require('crypto');
 var childProcess = require('child_process');
 
+function calculateBlobId(content) {
+  var header  = 'blob ' + content.length + '\0';
+  var store   = header + content;
+  var shasum  = crypto.createHash('sha1');
+  shasum.update(store);
+  return shasum.digest("hex");
+}
+
 module.exports = {
 
   head: function(cb) {
@@ -41,12 +49,21 @@ module.exports = {
     });
   },
 
-  calculateBlobId: function(content) {
-    var header  = 'blob ' + content.length + '\0';
-    var store   = header + content;
-    var shasum  = crypto.createHash('sha1');
-    shasum.update(store);
-    return shasum.digest("hex");
-  }
+  calculateBlobId: calculateBlobId,
+
+  blobId: function(path, content) {
+    var stdout, returnBlobId = null;
 
+    try {
+      stdout = childProcess.execSync("git hash-object " + path, { stdio: [0, "pipe", "ignore"] });
+    } catch (e) { }
+
+    if (stdout) {
+      returnBlobId = stdout.toString().trim();
+    } else {
+      returnBlobId = calculateBlobId(content);
+    }
+
+    return returnBlobId;
+  }
 };