tools: Add pre-commit support.

Tweak the existing codeformat.py and verifygitlog.py to allow them to be
easily called by pre-commit.

(This turned out to be easier than using any existing pre-commit hooks,
without making subtle changes in the formatting.)

This work was funded through GitHub Sponsors.

Signed-off-by: Angus Gratton <angus@redyak.com.au>

tools/verifygitlog.py

@@ -7,6 +7,8 @@ import sys
 verbosity = 0  # Show what's going on, 0 1 or 2.
 suggestions = 1  # Set to 0 to not include lengthy suggestions in error messages.
 
+ignore_prefixes = []
+
 
 def verbose(*args):
     if verbosity:
@@ -18,6 +20,22 @@ def very_verbose(*args):
         print(*args)
 
 
+class ErrorCollection:
+    # Track errors and warnings as the program runs
+    def __init__(self):
+        self.has_errors = False
+        self.has_warnings = False
+        self.prefix = ""
+
+    def error(self, text):
+        print("error: {}{}".format(self.prefix, text))
+        self.has_errors = True
+
+    def warning(self, text):
+        print("warning: {}{}".format(self.prefix, text))
+        self.has_warnings = True
+
+
 def git_log(pretty_format, *args):
     # Delete pretty argument from user args so it doesn't interfere with what we do.
     args = ["git", "log"] + [arg for arg in args if "--pretty" not in args]
@@ -28,83 +46,88 @@ def git_log(pretty_format, *args):
         yield line.decode().rstrip("\r\n")
 
 
-def verify(sha):
+def verify(sha, err):
     verbose("verify", sha)
-    errors = []
-    warnings = []
-
-    def error_text(err):
-        return "commit " + sha + ": " + err
-
-    def error(err):
-        errors.append(error_text(err))
-
-    def warning(err):
-        warnings.append(error_text(err))
+    err.prefix = "commit " + sha + ": "
 
     # Author and committer email.
     for line in git_log("%ae%n%ce", sha, "-n1"):
         very_verbose("email", line)
         if "noreply" in line:
-            error("Unwanted email address: " + line)
+            err.error("Unwanted email address: " + line)
 
     # Message body.
     raw_body = list(git_log("%B", sha, "-n1"))
+    verify_message_body(raw_body, err)
+
+
+def verify_message_body(raw_body, err):
     if not raw_body:
-        error("Message is empty")
-        return errors, warnings
+        err.error("Message is empty")
+        return
 
     # Subject line.
     subject_line = raw_body[0]
+    for prefix in ignore_prefixes:
+        if subject_line.startswith(prefix):
+            verbose("Skipping ignored commit message")
+            return
     very_verbose("subject_line", subject_line)
     subject_line_format = r"^[^!]+: [A-Z]+.+ .+\.$"
     if not re.match(subject_line_format, subject_line):
-        error("Subject line should match " + repr(subject_line_format) + ": " + subject_line)
+        err.error("Subject line should match " + repr(subject_line_format) + ": " + subject_line)
     if len(subject_line) >= 73:
-        error("Subject line should be 72 or less characters: " + subject_line)
+        err.error("Subject line should be 72 or less characters: " + subject_line)
 
     # Second one divides subject and body.
     if len(raw_body) > 1 and raw_body[1]:
-        error("Second message line should be empty: " + raw_body[1])
+        err.error("Second message line should be empty: " + raw_body[1])
 
     # Message body lines.
     for line in raw_body[2:]:
         # Long lines with URLs are exempt from the line length rule.
         if len(line) >= 76 and "://" not in line:
-            error("Message lines should be 75 or less characters: " + line)
+            err.error("Message lines should be 75 or less characters: " + line)
 
     if not raw_body[-1].startswith("Signed-off-by: ") or "@" not in raw_body[-1]:
-        warning("Message should be signed-off")
-
-    return errors, warnings
+        err.warning("Message should be signed-off")
 
 
 def run(args):
     verbose("run", *args)
-    has_errors = False
-    has_warnings = False
-    for sha in git_log("%h", *args):
-        errors, warnings = verify(sha)
-        has_errors |= any(errors)
-        has_warnings |= any(warnings)
-        for err in errors:
-            print("error:", err)
-        for err in warnings:
-            print("warning:", err)
-    if has_errors or has_warnings:
+
+    err = ErrorCollection()
+
+    if "--check-file" in args:
+        filename = args[-1]
+        verbose("checking commit message from", filename)
+        with open(args[-1]) as f:
+            lines = [line.rstrip("\r\n") for line in f]
+            verify_message_body(lines, err)
+    else:  # Normal operation, pass arguments to git log
+        for sha in git_log("%h", *args):
+            verify(sha, err)
+
+    if err.has_errors or err.has_warnings:
         if suggestions:
             print("See https://github.com/micropython/micropython/blob/master/CODECONVENTIONS.md")
     else:
         print("ok")
-    if has_errors:
+    if err.has_errors:
         sys.exit(1)
 
 
 def show_help():
-    print("usage: verifygitlog.py [-v -n -h] ...")
+    print("usage: verifygitlog.py [-v -n -h --check-file] ...")
     print("-v  : increase verbosity, can be speficied multiple times")
     print("-n  : do not print multi-line suggestions")
     print("-h  : print this help message and exit")
+    print(
+        "--check-file : Pass a single argument which is a file containing a candidate commit message"
+    )
+    print(
+        "--ignore-rebase : Skip checking commits with git rebase autosquash prefixes or WIP as a prefix"
+    )
     print("... : arguments passed to git log to retrieve commits to verify")
     print("      see https://www.git-scm.com/docs/git-log")
     print("      passing no arguments at all will verify all commits")
@@ -117,6 +140,10 @@ if __name__ == "__main__":
     args = sys.argv[1:]
     verbosity = args.count("-v")
     suggestions = args.count("-n") == 0
+    if "--ignore-rebase" in args:
+        args.remove("--ignore-rebase")
+        ignore_prefixes = ["squash!", "fixup!", "amend!", "WIP"]
+
     if "-h" in args:
         show_help()
     else: