bot_update: refactor giant git_checkout into two.

Change-Id: I2c023a538bfe62955238b39034ed7460286789e5
Reviewed-on: https://chromium-review.googlesource.com/771454
Reviewed-by: Jao-ke Chin-Lee <jchinlee@chromium.org>
Commit-Queue: Andrii Shyshkalov <tandrii@chromium.org>

recipes/recipe_modules/bot_update/resources/bot_update.py

@@ -561,7 +561,7 @@ def _maybe_break_locks(checkout_path):
           raise
 
 
-def git_checkout(solutions, revisions, shallow, refs, git_cache_dir,
+def git_checkouts(solutions, revisions, shallow, refs, git_cache_dir,
                   cleanup_dir):
   build_dir = os.getcwd()
   # Before we do anything, break all git_cache locks.
@@ -574,6 +574,18 @@ def git_checkout(solutions, revisions, shallow, refs, git_cache_dir,
         raise Exception('%s exists after cache unlock' % filename)
   first_solution = True
   for sln in solutions:
+    _git_checkout(sln, build_dir, revisions, shallow, refs, git_cache_dir,
+                  cleanup_dir)
+    if first_solution:
+      git_ref = git('log', '--format=%H', '--max-count=1',
+                    cwd=path.join(build_dir, sln['name'])
+                ).strip()
+    first_solution = False
+  return git_ref
+
+
+def _git_checkout(sln, build_dir, revisions, shallow, refs, git_cache_dir,
+                  cleanup_dir):
   # Just in case we're hitting a different git server than the one from
   # which the target revision was polled, we retry some.
   done = False
@@ -655,12 +667,6 @@ def git_checkout(solutions, revisions, shallow, refs, git_cache_dir,
 
   git('clean', '-dff', cwd=sln_dir)
 
-    if first_solution:
-      git_ref = git('log', '--format=%H', '--max-count=1',
-                    cwd=sln_dir).strip()
-    first_solution = False
-  return git_ref
-
 
 def _download(url):
   """Fetch url and return content, with retries for flake."""
@@ -833,7 +839,7 @@ def ensure_checkout(solutions, revisions, first_sln, target_os, target_os_only,
   # invoking DEPS.
   print 'Fetching Git checkout'
 
-  git_ref = git_checkout(solutions, revisions, shallow, refs, git_cache_dir,
+  git_ref = git_checkouts(solutions, revisions, shallow, refs, git_cache_dir,
                           cleanup_dir)
 
   print '===Processing patch solutions==='