Reference .git/index as a dependency of commit_id.

Any time the git index changes, we will re-run the commit id hook.
This will ensure we never are left with stale commit ids from
other git commits.

BUG=angle:626

Change-Id: I03c37225fb902b6c1801e8f993d767122e8bfeb6
Reviewed-on: https://chromium-review.googlesource.com/197723
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>

projects/src/commit_id.vcxproj

@@ -101,6 +101,9 @@
   </ItemDefinitionGroup>
   <ItemGroup>
     <None Include="..\..\src\angle.gyp"/>
+    <None Include="..\..\.git\index">
+      <ExcludedFromBuild>true</ExcludedFromBuild>
+    </None>
   </ItemGroup>
   <ItemGroup>
     <CustomBuild Include="$(OutDir)obj\global_intermediate\commit_id.bat">
@@ -108,6 +111,7 @@
       <Command>call call $(OutDir)obj\global_intermediate\commit_id.bat &quot;$(OutDir)obj\global_intermediate&quot;</Command>
       <Message>Generating commit ID header...</Message>
       <Outputs>$(OutDir)obj\global_intermediate\commit.h</Outputs>
+      <AdditionalInputs>..\..\.git\index</AdditionalInputs>
     </CustomBuild>
   </ItemGroup>
   <ItemGroup>

projects/src/commit_id.vcxproj.filters

@@ -19,6 +19,12 @@
     <Filter Include="..\..\src">
       <UniqueIdentifier>{8CDEE807-BC53-E450-C8B8-4DEBB66742D4}</UniqueIdentifier>
     </Filter>
+    <Filter Include="..\..\.git">
+      <UniqueIdentifier>{3C74FDB1-3FB1-8FA9-1073-A344751C6694}</UniqueIdentifier>
+    </Filter>
+    <Filter Include="..\..\.git\_excluded_files">
+      <UniqueIdentifier>{158E591E-B6EA-0C85-8F5A-18EAFA09B4CE}</UniqueIdentifier>
+    </Filter>
   </ItemGroup>
   <ItemGroup>
     <None Include="$(OutDir)obj\global_intermediate\commit_id.bat">
@@ -27,5 +33,8 @@
     <None Include="..\..\src\angle.gyp">
       <Filter>..\..\src</Filter>
     </None>
+    <None Include="..\..\.git\index">
+      <Filter>..\..\.git\_excluded_files</Filter>
+    </None>
   </ItemGroup>
 </Project>

src/angle.gypi

@@ -43,19 +43,19 @@
                             'action_name': 'Generate Commit ID Header',
                             'message': 'Generating commit ID header...',
                             'msvs_cygwin_shell': 0,
-                            'inputs': [ '<(SHARED_INTERMEDIATE_DIR)/commit_id.bat' ],
+                            'inputs': [ '<(SHARED_INTERMEDIATE_DIR)/commit_id.bat', '<(angle_path)/.git/index' ],
                             'outputs': [ '<(SHARED_INTERMEDIATE_DIR)/commit.h' ],
                             'action': [ '<(SHARED_INTERMEDIATE_DIR)/commit_id.bat', '<(SHARED_INTERMEDIATE_DIR)' ],
                         },
                     ],
                 },
-                {
+                { # OS != win
                     'actions':
                     [
                         {
                             'action_name': 'Generate Commit ID Header',
                             'message': 'Generating commit ID header...',
-                            'inputs': [ '<(SHARED_INTERMEDIATE_DIR)/commit_id.py' ],
+                            'inputs': [ '<(SHARED_INTERMEDIATE_DIR)/commit_id.py', '<(angle_path)/.git/index' ],
                             'outputs': [ '<(SHARED_INTERMEDIATE_DIR)/commit.h' ],
                             'action': [ 'python', '<(SHARED_INTERMEDIATE_DIR)/commit_id.py', '<(SHARED_INTERMEDIATE_DIR)/commit.h' ],
                         },