bot_update: default to non-shallow checkouts.

shallow mode is a special git mode that only checks out a shallow copy
of git so the full history is not downloaded. It is not well supported
by googlesource.com servers because git has to do a giant negotiation
with the server and transmit every single commit that the local checkout
has or doesn't have (instead of just the latest commit of each ref),
which ends up taking more than 10x longer than a non-shallow checkout.

R=ehmaldonado, hinoka, iannucci

Recipe-Nontrivial-Roll: infra
Recipe-Nontrivial-Roll: build
Recipe-Nontrivial-Roll: build_limited_scripts_slave
Bug: 855137
Change-Id: I5f9e31f8b2730cf80b79bfd0e08201c33eb942f5
Reviewed-on: https://chromium-review.googlesource.com/1110450
Commit-Queue: Andrii Shyshkalov <tandrii@chromium.org>
Reviewed-by: Ryan Tseng <hinoka@chromium.org>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>

recipes/README.recipes.md

@@ -53,7 +53,7 @@ Wrapper for easy calling of bot_update.
 Deapplies a patch, taking care of DEPS and solution revisions properly.
     
 
-— **def [ensure\_checkout](/recipes/recipe_modules/bot_update/api.py#68)(self, gclient_config=None, suffix=None, patch=True, update_presentation=True, patch_root=None, no_shallow=False, with_branch_heads=False, with_tags=False, refs=None, patch_oauth2=None, oauth2_json=None, use_site_config_creds=None, clobber=False, root_solution_revision=None, rietveld=None, issue=None, patchset=None, gerrit_no_reset=False, gerrit_no_rebase_patch_ref=False, disable_syntax_validation=False, manifest_name=None, \*\*kwargs):**
+— **def [ensure\_checkout](/recipes/recipe_modules/bot_update/api.py#68)(self, gclient_config=None, suffix=None, patch=True, update_presentation=True, patch_root=None, no_shallow=True, with_branch_heads=False, with_tags=False, refs=None, patch_oauth2=None, oauth2_json=None, use_site_config_creds=None, clobber=False, root_solution_revision=None, rietveld=None, issue=None, patchset=None, gerrit_no_reset=False, gerrit_no_rebase_patch_ref=False, disable_syntax_validation=False, manifest_name=None, \*\*kwargs):**
 
 Args:
   gclient_config: The gclient configuration to use when running bot_update.

recipes/recipe_modules/bot_update/api.py

@@ -67,7 +67,7 @@ class BotUpdateApi(recipe_api.RecipeApi):
 
   def ensure_checkout(self, gclient_config=None, suffix=None,
                       patch=True, update_presentation=True,
-                      patch_root=None, no_shallow=False,
+                      patch_root=None, no_shallow=True,
                       with_branch_heads=False, with_tags=False, refs=None,
                       patch_oauth2=None, oauth2_json=None,
                       use_site_config_creds=None, clobber=False,
@@ -208,8 +208,8 @@ class BotUpdateApi(recipe_api.RecipeApi):
 
     if clobber:
       cmd.append('--clobber')
-    if no_shallow:
-      cmd.append('--no_shallow')
+    if no_shallow is False:
+      cmd.append('--maybe_shallow')
     if with_branch_heads or cfg.with_branch_heads:
       cmd.append('--with_branch_heads')
     if with_tags or cfg.with_tags:

recipes/recipe_modules/bot_update/examples/full.expected/no_shallow.json → recipes/recipe_modules/bot_update/examples/full.expected/shallow.json

@@ -18,7 +18,7 @@
       "/path/to/tmp/json",
       "--revision",
       "src@HEAD",
-      "--no_shallow",
+      "--maybe_shallow",
       "--disable-syntax-validation"
     ],
     "env_prefixes": {

recipes/recipe_modules/bot_update/examples/full.py

@@ -40,7 +40,7 @@ def RunSteps(api):
 
   patch = api.properties.get('patch', True)
   clobber = True if api.properties.get('clobber') else False
-  no_shallow = True if api.properties.get('no_shallow') else False
+  no_shallow = True if api.properties.get('no_shallow', 1) else False
   with_branch_heads = api.properties.get('with_branch_heads', False)
   with_tags = api.properties.get('with_tags', False)
   refs = api.properties.get('refs', [])
@@ -148,8 +148,8 @@ def GenTests(api):
       rietveld='https://rietveld.example.com/',
       fail_patch='download'
   ) + api.step_data('bot_update', retcode=87)
-  yield api.test('no_shallow') + api.properties(
-      no_shallow=1
+  yield api.test('shallow') + api.properties(
+      no_shallow=0
   )
   yield api.test('clobber') + api.properties(
       clobber=1

recipes/recipe_modules/bot_update/resources/bot_update.py

@@ -1038,9 +1038,9 @@ def parse_args():
                    help='Delete checkout first, always')
   parse.add_option('--output_json',
                    help='Output JSON information into a specified file')
-  parse.add_option('--no_shallow', action='store_true',
-                   help='Bypass disk detection and never shallow clone. '
-                        'Does not override the --shallow flag')
+  parse.add_option('--maybe_shallow', action='store_true',
+                   help='Enables turning on shallow mode if total disk '
+                        'space is low.')
   parse.add_option('--refs', action='append',
                    help='Also fetch this refspec for the main solution(s). '
                         'Eg. +refs/branch-heads/*')
@@ -1126,7 +1126,7 @@ def prepare(options, git_slns, active):
                                            total_disk_space_gb,
                                            percent_used)
   shallow = (total_disk_space < SHALLOW_CLONE_THRESHOLD
-             and not options.no_shallow)
+             and options.maybe_shallow)
 
   # The first solution is where the primary DEPS file resides.
   first_sln = dir_names[0]