[IMP] runbot_merge: inline stage_into, remove working copy

Turns out we can (most likely) do all the work in the local main repo
directly, so there is no need for the separate working copy, or the
exist stack, and thus no need for a separate function to be
context-managed.

Should have yagni'd and waited to setup the working copy stuff... oh
well.

runbot_merge/models/stagings_create.py

@@ -41,7 +41,6 @@ class StagingSlice:
     """
     gh: github.GH
     head: str
-    working_copy: git.Repo[CompletedProcess]
     repo: git.Repo[CompletedProcess]
 
 
@@ -84,43 +83,7 @@ def try_staging(branch: Branch) -> Optional[Stagings]:
     else: # p=2
         batched_prs = [pr_ids for _, pr_ids in takewhile(lambda r: r[0] == priority, rows)]
 
-    with contextlib.ExitStack() as cleanup:
-        return stage_into(branch, batched_prs, cleanup)
-
-
-def ready_prs(for_branch: Branch) -> List[Tuple[int, PullRequests]]:
-    env = for_branch.env
-    env.cr.execute("""
-    SELECT
-      min(pr.priority) as priority,
-      array_agg(pr.id) AS match
-    FROM runbot_merge_pull_requests pr
-    WHERE pr.target = any(%s)
-      -- exclude terminal states (so there's no issue when
-      -- deleting branches & reusing labels)
-      AND pr.state != 'merged'
-      AND pr.state != 'closed'
-    GROUP BY
-        pr.target,
-        CASE
-            WHEN pr.label SIMILAR TO '%%:patch-[[:digit:]]+'
-                THEN pr.id::text
-            ELSE pr.label
-        END
-    HAVING
-        bool_or(pr.state = 'ready') or bool_or(pr.priority = 0)
-    ORDER BY min(pr.priority), min(pr.id)
-    """, [for_branch.ids])
-    browse = env['runbot_merge.pull_requests'].browse
-    return [(p, browse(ids)) for p, ids in env.cr.fetchall()]
-
-
-def stage_into(
-        branch: Branch,
-        batched_prs: List[PullRequests],
-        cleanup: contextlib.ExitStack,
-) -> Optional[Stagings]:
-    original_heads, staging_state = staging_setup(branch, batched_prs, cleanup)
+    original_heads, staging_state = staging_setup(branch, batched_prs)
 
     staged = stage_batches(branch, batched_prs, staging_state)
 
@@ -225,10 +188,36 @@ For-Commit-Id: {it.head}
     return st
 
 
+def ready_prs(for_branch: Branch) -> List[Tuple[int, PullRequests]]:
+    env = for_branch.env
+    env.cr.execute("""
+    SELECT
+      min(pr.priority) as priority,
+      array_agg(pr.id) AS match
+    FROM runbot_merge_pull_requests pr
+    WHERE pr.target = any(%s)
+      -- exclude terminal states (so there's no issue when
+      -- deleting branches & reusing labels)
+      AND pr.state != 'merged'
+      AND pr.state != 'closed'
+    GROUP BY
+        pr.target,
+        CASE
+            WHEN pr.label SIMILAR TO '%%:patch-[[:digit:]]+'
+                THEN pr.id::text
+            ELSE pr.label
+        END
+    HAVING
+        bool_or(pr.state = 'ready') or bool_or(pr.priority = 0)
+    ORDER BY min(pr.priority), min(pr.id)
+    """, [for_branch.ids])
+    browse = env['runbot_merge.pull_requests'].browse
+    return [(p, browse(ids)) for p, ids in env.cr.fetchall()]
+
+
 def staging_setup(
         target: Branch,
         batched_prs: List[PullRequests],
-        cleanup: contextlib.ExitStack
 ) -> Tuple[Dict[Repository, str], StagingState]:
     """Sets up the staging:
 
@@ -237,7 +226,6 @@ def staging_setup(
     - generates working copy for each repository with the target branch
     """
     all_prs: PullRequests = target.env['runbot_merge.pull_requests'].concat(*batched_prs)
-    cache_dir = user_cache_dir('mergebot')
     staging_state = {}
     original_heads = {}
     for repo in target.project_id.repo_ids.having_branch(target):
@@ -257,14 +245,8 @@ def staging_setup(
             f'+refs/heads/{target.name}:refs/heads/{target.name}',
             *(pr.head for pr in all_prs if pr.repository == repo)
         )
-        Path(cache_dir, repo.name).parent.mkdir(parents=True, exist_ok=True)
-        d = cleanup.enter_context(tempfile.TemporaryDirectory(
-            prefix=f'{repo.name}-{target.name}-staging',
-            dir=cache_dir,
-        ))
-        working_copy = source.clone(d, branch=target.name)
         original_heads[repo] = head
-        staging_state[repo] = StagingSlice(gh=gh, head=head, working_copy=working_copy, repo=source)
+        staging_state[repo] = StagingSlice(gh=gh, head=head, repo=source)
 
     return original_heads, staging_state