lint: Add linter rules for markdown.

.gitignore

@@ -134,4 +134,5 @@ dmypy.json
 
 # Exclusions
 
-!src/xkcd_pass/lib/
+!src/xkcd_pass/lib/
+!tools/lib

tools/lib/custom_check.py

@@ -0,0 +1,53 @@
+from typing import List
+
+from zulint.custom_rules import Rule, RuleList
+
+trailing_whitespace_rule: "Rule" = {
+    "pattern": r"\s+$",
+    "strip": "\n",
+    "description": "Fix trailing whitespace",
+}
+whitespace_rules: List["Rule"] = [
+    # This linter should be first since bash_rules depends on it.
+    trailing_whitespace_rule,
+]
+
+markdown_whitespace_rules: List["Rule"] = [
+    *(rule for rule in whitespace_rules if rule["pattern"] != r"\s+$"),
+    # Two spaces trailing a line with other content is okay--it's a Markdown line break.
+    # This rule finds one space trailing a non-space, three or more trailing spaces, and
+    # spaces on an empty line.
+    {
+        "pattern": r"((?<!\s)\s$)|(\s\s\s+$)|(^\s+$)",
+        "strip": "\n",
+        "description": "Fix trailing whitespace",
+    },
+    {
+        "pattern": "^#+[A-Za-z0-9]",
+        "strip": "\n",
+        "description": "Missing space after # in heading",
+        "good_lines": ["### some heading", "# another heading"],
+        "bad_lines": ["###some heading", "#another heading"],
+    },
+]
+
+markdown_rules = RuleList(
+    langs=["md"],
+    rules=[
+        *markdown_whitespace_rules,
+        {
+            "pattern": r"\[(?P<url>[^\]]+)\]\((?P=url)\)",
+            "description": "Linkified Markdown URLs should use cleaner <http://example.com> syntax.",
+        },
+        {
+            "pattern": r"\][(][^#h]",
+            "include_only": {"README.md"},
+            "description": "Use absolute links from docs served by GitHub",
+        },
+    ],
+    max_length=120,
+)
+
+non_py_rules = [
+    markdown_rules,
+]

tools/lib/gitlint-rules.py

@@ -0,0 +1,110 @@
+from typing import List
+
+from gitlint.git import GitCommit
+from gitlint.rules import CommitMessageTitle, LineRule, RuleViolation
+
+# Word list from https://github.com/m1foley/fit-commit
+# Copyright (c) 2015 Mike Foley
+# License: MIT
+# Ref: fit_commit/validators/tense.rb
+TENSE_DATA = [
+    (["adds", "adding", "added"], "add"),
+    (["allows", "allowing", "allowed"], "allow"),
+    (["amends", "amending", "amended"], "amend"),
+    (["bumps", "bumping", "bumped"], "bump"),
+    (["calculates", "calculating", "calculated"], "calculate"),
+    (["changes", "changing", "changed"], "change"),
+    (["cleans", "cleaning", "cleaned"], "clean"),
+    (["commits", "committing", "committed"], "commit"),
+    (["corrects", "correcting", "corrected"], "correct"),
+    (["creates", "creating", "created"], "create"),
+    (["darkens", "darkening", "darkened"], "darken"),
+    (["disables", "disabling", "disabled"], "disable"),
+    (["displays", "displaying", "displayed"], "display"),
+    (["documents", "documenting", "documented"], "document"),
+    (["drys", "drying", "dryed"], "dry"),
+    (["ends", "ending", "ended"], "end"),
+    (["enforces", "enforcing", "enforced"], "enforce"),
+    (["enqueues", "enqueuing", "enqueued"], "enqueue"),
+    (["extracts", "extracting", "extracted"], "extract"),
+    (["finishes", "finishing", "finished"], "finish"),
+    (["fixes", "fixing", "fixed"], "fix"),
+    (["formats", "formatting", "formatted"], "format"),
+    (["guards", "guarding", "guarded"], "guard"),
+    (["handles", "handling", "handled"], "handle"),
+    (["hides", "hiding", "hid"], "hide"),
+    (["increases", "increasing", "increased"], "increase"),
+    (["ignores", "ignoring", "ignored"], "ignore"),
+    (["implements", "implementing", "implemented"], "implement"),
+    (["improves", "improving", "improved"], "improve"),
+    (["keeps", "keeping", "kept"], "keep"),
+    (["kills", "killing", "killed"], "kill"),
+    (["makes", "making", "made"], "make"),
+    (["merges", "merging", "merged"], "merge"),
+    (["moves", "moving", "moved"], "move"),
+    (["permits", "permitting", "permitted"], "permit"),
+    (["prevents", "preventing", "prevented"], "prevent"),
+    (["pushes", "pushing", "pushed"], "push"),
+    (["rebases", "rebasing", "rebased"], "rebase"),
+    (["refactors", "refactoring", "refactored"], "refactor"),
+    (["removes", "removing", "removed"], "remove"),
+    (["renames", "renaming", "renamed"], "rename"),
+    (["reorders", "reordering", "reordered"], "reorder"),
+    (["replaces", "replacing", "replaced"], "replace"),
+    (["requires", "requiring", "required"], "require"),
+    (["restores", "restoring", "restored"], "restore"),
+    (["sends", "sending", "sent"], "send"),
+    (["sets", "setting"], "set"),
+    (["separates", "separating", "separated"], "separate"),
+    (["shows", "showing", "showed"], "show"),
+    (["simplifies", "simplifying", "simplified"], "simplify"),
+    (["skips", "skipping", "skipped"], "skip"),
+    (["sorts", "sorting"], "sort"),
+    (["speeds", "speeding", "sped"], "speed"),
+    (["starts", "starting", "started"], "start"),
+    (["supports", "supporting", "supported"], "support"),
+    (["takes", "taking", "took"], "take"),
+    (["testing", "tested"], "test"),  # "tests" excluded to reduce false negatives
+    (["truncates", "truncating", "truncated"], "truncate"),
+    (["updates", "updating", "updated"], "update"),
+    (["uses", "using", "used"], "use"),
+]
+
+TENSE_CORRECTIONS = {word: imperative for words, imperative in TENSE_DATA for word in words}
+
+
+class ImperativeMood(LineRule):
+    """This rule will enforce that the commit message title uses imperative
+    mood. This is done by checking if the first word is in `WORD_SET`, if so
+    show the word in the correct mood."""
+
+    name = "title-imperative-mood"
+    id = "Z1"
+    target = CommitMessageTitle
+
+    error_msg = (
+        "The first word in commit title should be in imperative mood "
+        '("{word}" -> "{imperative}"): "{title}"'
+    )
+
+    def validate(self, line: str, commit: GitCommit) -> List[RuleViolation]:
+        violations = []
+
+        # Ignore the section tag (ie `<section tag>: <message body>.`)
+        words = line.split(": ", 1)[-1].split()
+        first_word = words[0].lower()
+
+        if first_word in TENSE_CORRECTIONS:
+            imperative = TENSE_CORRECTIONS[first_word]
+            violation = RuleViolation(
+                self.id,
+                self.error_msg.format(
+                    word=first_word,
+                    imperative=imperative,
+                    title=commit.message.title,
+                ),
+            )
+
+            violations.append(violation)
+
+        return violations

tools/lint

@@ -4,6 +4,7 @@ from __future__ import absolute_import, print_function
 import argparse
 import re
 
+from lib.custom_check import non_py_rules
 from zulint.command import LinterConfig, add_default_linter_arguments
 from zulint.custom_rules import RuleList
 from zulint.linters import run_pyflakes
@@ -92,6 +93,14 @@ def run():
         failed = trailing_whitespace_rule.check(by_lang, verbose=args.verbose)
         return 1 if failed else 0
 
+    @linter_config.lint
+    def custom_nonpy() -> int:
+        """Runs custom checks for non-python files (config: tools/lib/custom_check.py)"""
+        failed = False
+        for rule in non_py_rules:
+            failed = failed or rule.check(by_lang, verbose=args.verbose)
+        return 1 if failed else 0
+
     @linter_config.lint
     def pyflakes():
         # type: () -> int