Generalize patch_project to patch root conversion.

recipe_modules/gclient/config.py

Index: recipe_modules/gclient/config.py
diff --git a/recipe_modules/gclient/config.py b/recipe_modules/gclient/config.py
index c300edd506d54e52808063ac576d6ba3c322bcbe..33079822b3e849e3b9c712ee0ea23fe8d0fccc8d 100644
--- a/recipe_modules/gclient/config.py
+++ b/recipe_modules/gclient/config.py
@@ -30,6 +30,18 @@ def BaseConfig(USE_MIRROR=True, GIT_MODE=False, CACHE_DIR=None,
         revision = Single(
             (basestring, gclient_api.RevisionResolver),
             required=False, hidden=True),
+
+        # Maps patch_project to (solution, revision).
+        #  - solution is used also as patch root.
+        #  - if revision is given, it's passed to bot_update.
+        # This is essentially a whitelist of which projects inside a solution
+        # can be patched automatically by bot_update based on PATCH_PROJECT
+        # property.
+        # For example, bare chromium solution has this entry in patch_projects
+        #     'v8': ('v8', 'HEAD')

[Michael Achenbach, 2016/04/25 09:32:42]

Stay in sync with below (includes src). Maybe provide a less intuitive example
where the solution and project names don't match.

[tandrii(chromium), 2016/04/25 11:39:50]

Done.

+        # then a v8 patch can be applied on a chromium checkout after synching v8
+        # to it's master HEAD.
+        patch_projects = Dict(value_type=tuple),
       )
     ),
     deps_os = Dict(value_type=basestring),
@@ -146,18 +158,16 @@ def chromium_bare(c):
   p['parent_got_v8_revision'] = 'v8_revision'
   p['parent_got_webrtc_revision'] = 'webrtc_revision'
 
-  # Patch project revisions are applied whenever patch_project is set. E.g. if
-  # a v8 stand-alone patch is sent to a chromium trybot, patch_project is v8
-  # and can be used to sync v8 to HEAD instead of the pinned chromium
-  # version.
-  patch_project_revisions = {
-    'v8': ('src/v8', 'HEAD'),
-  }
-
-  patch_revision = patch_project_revisions.get(c.PATCH_PROJECT)
-  # TODO(phajdan.jr): Move to proper repo and add coverage.
-  if patch_revision:  # pragma: no cover
-    c.revisions[patch_revision[0]] = patch_revision[1]
+  p = s.patch_projects

[Michael Achenbach, 2016/04/25 09:32:42]

I'd make this global, i.e. c.patch_projects, as the solution name is part of the
first item of the tuples.

[tandrii(chromium), 2016/04/25 11:39:50]

Done.

+  p['v8'] = ('src/v8', 'HEAD')

[tandrii(chromium), 2016/04/22 15:59:10]

for gerrit, this row would be duplicated with
  'v8/v8' = ('src/v8', 'HEAD')

+  p['angle/angle'] = ('src/third_party/angle', None)

[tandrii(chromium), 2016/04/22 15:59:10]

this is how gerrit looks.

+  p['blink'] = ('src/third_party/WebKit', None)

[tandrii(chromium), 2016/04/22 15:59:10]

machenbach@ i decided to specify the the full path here instead of omitting src
for consistency, as that's what code 15 lines above does anyway.

[Michael Achenbach, 2016/04/25 09:32:42]

Does blink still exist in this context? Keep it around if the old code had it.

[tandrii(chromium), 2016/04/25 11:39:50]

kept as is, but yes, i think i'll clean it up with all the todos in subsequent
CLs.

+  # TODO(tandrii): can this be done automatically for all solutions,
+  # instead of copy-pasting these 3 lines to very solution?
+  # If so, remove occurrencies in this file.
+  path, revision = s.patch_projects.get(c.PATCH_PROJECT, (None, None))

[Michael Achenbach, 2016/04/25 09:32:42]

Move to bot_update ensure_checkout and maybe to gclient sync.

[tandrii(chromium), 2016/04/25 11:39:50]

Done.

+  if path and revision:
+    c.revisions[path] = revision
 
 @config_ctx(includes=['chromium_bare'])
 def chromium_empty(c):
@@ -538,6 +548,16 @@ def infra(c):
   soln.url = 'https://chromium.googlesource.com/infra/infra.git'
   c.got_revision_mapping['infra'] = 'got_revision'
 
+  p = soln.patch_projects
+  p['luci-py'] = ('infra/luci', 'HEAD')
+  p['recipes-py'] = ('infra/recipes-py', 'HEAD')
+  # TODO(tandrii): can this be done automatically for all solutions,
+  # instead of copy-pasting these 3 lines to very solution?
+  # If so, remove occurrencies in this file.
+  path, revision = soln.patch_projects.get(c.PATCH_PROJECT, (None, None))
+  if path and revision:
+    c.revisions[path] = revision
+
 @config_ctx(config_vars={'GIT_MODE': True})
 def infra_internal(c):  # pragma: no cover
   soln = c.solutions.add()
@@ -572,6 +592,7 @@ def luci_py(c):
   # luci-py is checked out as part of infra just to have appengine
   # pre-installed, as that's what luci-py PRESUBMIT relies on.
   c.revisions['infra'] = 'origin/master'
+  # TODO(tandrii): make use of c.patch_projects.
   c.revisions['infra/luci'] = (
       gclient_api.RevisionFallbackChain('origin/master'))
   m = c.got_revision_mapping
@@ -581,6 +602,7 @@ def luci_py(c):
 @config_ctx(includes=['infra'])
 def recipes_py(c):
   c.revisions['infra'] = 'origin/master'
+  # TODO(tandrii): make use of c.patch_projects.
   c.revisions['infra/recipes-py'] = (
       gclient_api.RevisionFallbackChain('origin/master'))
   m = c.got_revision_mapping
@@ -634,6 +656,7 @@ def angle_top_of_tree(c):  # pragma: no cover
 
   Sets up ToT instead of the DEPS-pinned revision for ANGLE.
   """
+  # TODO(tandrii): I think patch_projects in bare_chromium fixed this.
   c.solutions[0].revision = 'HEAD'
   c.revisions['src/third_party/angle'] = 'HEAD'