style: use import hooks everywhere

Align with Google style guides and `import hooks` as a module
rather than import symbols out of it.

Change-Id: I85a071ee73f8904ac33eae437d7853785762ba71
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/655846
Reviewed-by: Brian Gan <brgan@google.com>
Commit-Queue: Mike Frysinger <vapier@google.com>
Tested-by: Mike Frysinger <vapier@google.com>

subcmds/sync.py

@@ -60,7 +60,7 @@ import git_command
 import git_config
 import git_refs
 import git_superproject
-from hooks import RepoHook
+import hooks
 import manifest_xml
 import platform_utils
 import progress
@@ -900,7 +900,7 @@ later is required to fix a server side protocol bug.
             action="store_true",
             help=optparse.SUPPRESS_HELP,
         )
-        RepoHook.AddOptionGroup(p, "post-sync")
+        hooks.RepoHook.AddOptionGroup(p, "post-sync")
 
     def _GetBranch(self, manifest_project):
         """Returns the branch name for getting the approved smartsync manifest.
@@ -2568,7 +2568,7 @@ later is required to fix a server side protocol bug.
 
     def _RunPostSyncHook(self, opt, sync_duration_seconds=None):
         """Run post-sync hook if configured in manifest <repo-hooks>."""
-        hook = RepoHook.FromSubcmd(
+        hook = hooks.RepoHook.FromSubcmd(
             hook_type="post-sync",
             manifest=self.manifest,
             opt=opt,

subcmds/upload.py

@@ -24,7 +24,7 @@ import editor
 import error
 import git_refs
 import git_superproject
-from hooks import RepoHook
+import hooks
 from project import ReviewableBranch
 import repo_logging
 from subcmds.sync import LocalSyncState
@@ -381,7 +381,7 @@ Gerrit Code Review:  https://www.gerritcodereview.com/
             default=True,
             help="disable verifying ssl certs (unsafe)",
         )
-        RepoHook.AddOptionGroup(p, "pre-upload", allow_fix=True)
+        hooks.RepoHook.AddOptionGroup(p, "pre-upload", allow_fix=True)
 
     def _SingleBranch(self, opt, branch, people):
         project = branch.project
@@ -827,7 +827,7 @@ Gerrit Code Review:  https://www.gerritcodereview.com/
                 for (project, available) in pending
                 if project.manifest.topdir == manifest.topdir
             ]
-            hook = RepoHook.FromSubcmd(
+            hook = hooks.RepoHook.FromSubcmd(
                 hook_type="pre-upload",
                 manifest=manifest,
                 opt=opt,