Docserver: Use GitilesFileSystem instead of SubversionFileSystem

chrome/common/extensions/docs/server2/app_yaml_helper.py

Index: chrome/common/extensions/docs/server2/app_yaml_helper.py
diff --git a/chrome/common/extensions/docs/server2/app_yaml_helper.py b/chrome/common/extensions/docs/server2/app_yaml_helper.py
index d2bb706f97a7d133209336a17b48ef574b97f225..d965f96de67e9b25b82d8e6000fccaa76672058b 100644
--- a/chrome/common/extensions/docs/server2/app_yaml_helper.py
+++ b/chrome/common/extensions/docs/server2/app_yaml_helper.py
@@ -25,7 +25,7 @@ class AppYamlHelper(object):
                host_file_system_provider):
     self._store = object_store_creator.Create(
         AppYamlHelper,
-        category=host_file_system_provider.GetTrunk().GetIdentity(),
+        category=host_file_system_provider.GetMaster().GetIdentity(),
         start_empty=False)
     self._host_file_system_provider = host_file_system_provider
 
@@ -74,7 +74,7 @@ class AppYamlHelper(object):
     checked into the host file system.
     '''
     checked_in_app_version = AppYamlHelper.ExtractVersion(
-        self._host_file_system_provider.GetTrunk().ReadSingle(APP_YAML).Get())
+        self._host_file_system_provider.GetMaster().ReadSingle(APP_YAML).Get())
     if app_version == checked_in_app_version:
       return True
     if AppYamlHelper.IsGreater(app_version, checked_in_app_version):
@@ -100,6 +100,8 @@ class AppYamlHelper(object):
     return stored
 
   def _GetFirstRevisionGreaterThanImpl(self, app_version):
+    # XXX(ahernandez): Tricky. The 'version' of app.yaml coming from
+    # GitilesFileSystem is a blob ID.
     def get_app_yaml_revision(file_system):
       return int(file_system.Stat(APP_YAML).version)

[not at google - send to devlin, 2014/08/26 22:52:23]

Yeah int-ing this isn't going to work obviously. Could you make
GetPreviousCommitID take the commit to get the previous of? The implementation
of that for SubversionFileSystem would be just int-ify the ID then subtract 1.
The GitilesFileSystem implementation would need to look up the commit history
but that should be straightforward right?

The other place this is assumed to be an int is the "found == 0" call. I don't
even remember what that's supposed to be.

[ahernandez, 2014/08/26 23:35:56]

Does GetPreviousCommitID need to be implemented in SubversionFS? It's not being
used at all, and I thought it wasn't going to be used in the future either.
Yep, shouldn't be hard at all, I forgot the commit message has the revision
number.

[not at google - send to devlin, 2014/08/27 01:07:13]

I was assuming we'd implement all of this functionality which relies on
determining some commit order could use GetPreviousCommitID. I don't even know
if you'd need to look up revision numbers.

I.e. here we assume that the previous commit ID of |found| is |found - 1|.
Really it's GetPreviousCommitID(found), it just happens that Subversion uses
sequential commit IDs.

[Ken Rockot(use gerrit already), 2014/08/29 07:24:42]

So I'm spinning all of this context back up in my head. It seems like bad news
to really walk backwards through the entire commit history one by one. Couldn't
we just walk backwards through the app.yaml log? i.e.

https://chromium.googlesource.com/chromium/src/+log/master/chrome/common/exte...

Gitiles features that might make this awesomer/possible:

1. Log URLs like above should include a blob field in each log entry,
identifying the blob ID for the referenced file's state at each commit.

So three commits back (at commit ID d1f4a4550f63c4b5c9156f37066a7635c3cd00c6)
app.yaml has blob ID a4b5dc6825c7c2e9468031c5c6d75f2b06622b62 which corresponds
to version 3-39-4.

The third log entry from the JSON log above should include a
'blob'=='a4b5dc6825c7c2e9468031c5c6d75f2b06622b62' entry pair.

2. Support for raw blob fetching by blob ID, which does not yet exist to the
best of my knowledge. i.e. it would be nice to be able to fetch

https://chromium.googlesource.com/chromium/src/+blob/a4b5dc6825c7c2e9468031c5...

and just get a raw copy of app.yaml from commit
d1f4a4550f63c4b5c9156f37066a7635c3cd00c6, aka the one from 3 commits ago where
version is 3-39-4.

 
@@ -109,7 +111,7 @@ class AppYamlHelper(object):
       return AppYamlHelper.IsGreater(app_version_in_file_system, app_version)
 
     found = None
-    next_file_system = self._host_file_system_provider.GetTrunk()
+    next_file_system = self._host_file_system_provider.GetMaster()
 
     while has_greater_app_version(next_file_system):
       found = get_app_yaml_revision(next_file_system)
@@ -117,8 +119,8 @@ class AppYamlHelper(object):
       if found == 0:
         logging.warning('All revisions are greater than %s' % app_version)
         return 0
-      next_file_system = self._host_file_system_provider.GetTrunk(
-          revision=found - 1)
+      next_file_system = self._host_file_system_provider.GetMaster(
+          commit=next_file_system.GetPreviousCommitID().Get())
 
     if found is None:
       raise ValueError('All revisions are less than %s' % app_version)