Refactor tools/actions_local_runner.py to allow custom remote/branch names

Currently this script assumes origin/master as the branch for comparison when --changed-only flag is used.
Although this is reasonable for PyTorch build infrastructure, external contributors that fork PyTorch may have different remotes/branch names, such as upstream/master

Assuming users have a `origin` remote for their PyTorch fork and a `upstream` remote pointing to the original PyTorch repo

For external contributions, by running
```
    make quick_checks CHANGED_ONLY=--changed-only
    make flake8 CHANGED_ONLY=--changed-only
    make mypy CHANGED_ONLY=--changed-only
    make cmakelint CHANGED_ONLY=--changed-only
    make shellcheck CHANGED_ONLY=--changed-only
    make clang-tidy CHANGED_ONLY=--changed-only
    make quicklint -j ${CPUS} CHANGED_ONLY=--changed-only
```
would result in an incorrect git diff, forcing users to run a full test as opposed to just test changed files

This PR introduces a --ref_branch argument that allows users to specify an arbitrary branch to detect changes in their own PyTorch forks which may have a remote for the upstream PyTorch repo.

Given the proposed changes, this is how users could compare their changes to an arbitrary remote/branch
```
    make quick_checks CHANGED_ONLY=--changed-only REF_BRANCH=--ref_branch=upstream/master
    make flake8 CHANGED_ONLY=--changed-only REF_BRANCH=--ref_branch=upstream/master
    make mypy CHANGED_ONLY=--changed-only REF_BRANCH=--ref_branch=upstream/master
    make cmakelint CHANGED_ONLY=--changed-only REF_BRANCH=--ref_branch=upstream/master
    make shellcheck CHANGED_ONLY=--changed-only REF_BRANCH=--ref_branch=upstream/master
    make clang-tidy CHANGED_ONLY=--changed-only REF_BRANCH=--ref_branch=upstream/master
    make quicklint -j ${CPUS} CHANGED_ONLY=--changed-only REF_BRANCH=--ref_branch=upstream/master
```

This change is BC, as it assigns origin/master as default argument to all existing methods that handle branches
Pull Request resolved: https://github.com/pytorch/pytorch/pull/73387
Approved by: malfet

Makefile

@@ -47,6 +47,7 @@ shellcheck:
 		--step 'Extract scripts from GitHub Actions workflows'
 	@$(PYTHON) tools/actions_local_runner.py \
 		$(CHANGED_ONLY) \
+		$(REF_BRANCH) \
 		--job 'shellcheck'
 
 setup_lint:
@@ -94,11 +95,13 @@ quick_checks:
 flake8:
 	@$(PYTHON) tools/actions_local_runner.py \
 		$(CHANGED_ONLY) \
+		$(REF_BRANCH) \
 		--job 'flake8-py3'
 
 mypy:
 	@$(PYTHON) tools/actions_local_runner.py \
 		$(CHANGED_ONLY) \
+		$(REF_BRANCH) \
 		--job 'mypy'
 
 cmakelint:
@@ -110,6 +113,7 @@ cmakelint:
 clang-tidy:
 	@$(PYTHON) tools/actions_local_runner.py \
 		$(CHANGED_ONLY) \
+		$(REF_BRANCH) \
 		--job 'clang-tidy'
 
 toc:

tools/actions_local_runner.py

@@ -59,7 +59,7 @@ def git(args: List[str]) -> List[str]:
     return [line.strip() for line in lines]
 
 
-def find_changed_files() -> List[str]:
+def find_changed_files(ref_branch : str = "origin/master") -> List[str]:
     untracked = []
 
     for line in git(["status", "--porcelain"]):
@@ -74,7 +74,7 @@ def find_changed_files() -> List[str]:
     cached = git(["diff", "--cached", "--name-only"])
 
     # Committed
-    merge_base = git(["merge-base", "origin/master", "HEAD"])[0]
+    merge_base = git(["merge-base", ref_branch, "HEAD"])[0]
     diff_with_origin = git(["diff", "--name-only", merge_base, "HEAD"])
 
     # De-duplicate
@@ -334,10 +334,10 @@ class YamlStep(Check):
         return await shell_cmd(script, env=env)
 
 
-def changed_files() -> Optional[List[str]]:
+def changed_files(ref_branch : str = "origin/master") -> Optional[List[str]]:
     changed_files: Optional[List[str]] = None
     try:
-        changed_files = sorted(find_changed_files())
+        changed_files = sorted(find_changed_files(ref_branch))
     except Exception:
         # If the git commands failed for some reason, bail out and use the whole list
         print(
@@ -381,6 +381,9 @@ def main() -> None:
         "--no-quiet", help="output commands", action="store_true", default=False
     )
     parser.add_argument("--step", action="append", help="steps to run (in order)")
+    parser.add_argument("--ref_branch",
+                        default="origin/master",
+                        help="remote/branch used during comparison for --changed-only (default=origin/master")
     args = parser.parse_args()
 
     quiet = not args.no_quiet
@@ -396,7 +399,7 @@ def main() -> None:
 
         files = None
         if args.changed_only:
-            files = changed_files()
+            files = changed_files(args.ref_branch)
 
         checks = [ad_hoc_steps[args.job](files, quiet)]
     else: