dev: add commit linter workflow

Experimenting with an internal linter. Only trouble is, if Doom's CLI is
ever in a broken state, a contributor will have to know about
--no-verify option for git commit. This can be improved post CLI
rewrite.

.github/workflows/lint.yml

@@ -0,0 +1,11 @@
+name: Commit linter
+on:
+  pull_request:
+jobs:
+  lint-commits:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2.3.1
+        with:
+          fetch-depth: 0
+      - run: bin/doom ci lint-commits HEAD~1

core/cli/ci.el

@@ -0,0 +1,172 @@
+;;; core/cli/ci.el -*- lexical-binding: t; -*-
+
+(defcli! ci (&optional target &rest args)
+  "TODO"
+  (unless target
+    (user-error "No CI target given"))
+  (if-let (fn (intern-soft (format "doom-cli--ci-%s" target)))
+      (apply fn args)
+    (user-error "No known CI target: %S" target)))
+
+
+;;
+;;;
+
+
+(defun doom-cli--ci-deploy-hooks ()
+  (let ((dir (doom-path doom-emacs-dir ".git/hooks"))
+        (default-directory doom-emacs-dir))
+    (make-directory dir 'parents)
+    (dolist (hook '("commit-msg"))
+      (let ((file (doom-path dir hook)))
+        (with-temp-file file
+          (insert "#!/usr/bin/env sh\n"
+                  (doom-path doom-emacs-dir "bin/doom")
+                  " --nocolor ci hook-" hook
+                  " \"$@\""))
+        (set-file-modes file #o700)
+        (print! (success "Created %s") (relpath file))))))
+
+
+;;
+;;; Git hooks
+
+(defvar doom-cli-commit-rules
+  (list (cons "^[^\n]\\{10,\\}\n"
+              "Commit summary is too short (<10) and should be more descriptive")
+
+        (cons "^\\(revert!?:[^\n]\\{,72\\}\\|[^\n]\\{,80\\}\\)\n"
+              "Commit summary too long; <=72 is ideal, 80 is max")
+
+        (cons (concat
+               "^\\("
+               (regexp-opt
+                '("bump" "dev" "docs" "feat" "fix" "merge" "nit" "perf"
+                  "refactor" "release" "revert" "test" "tweak"))
+               "\\)!?[^ :]*: ")
+              "Invalid type")
+
+        (cons (lambda ()
+                (looking-at "^\\(bump\\|revert\\|release\\|merge\\)!?([^)]+):"))
+              "This commit type's scope goes after the colon, not before")
+
+        (cons (lambda ()
+                (when (looking-at "[^ :!(]+!?(\\([^)]+\\)): ")
+                  (not
+                   (string-match
+                    (string-join
+                     (cons (concat
+                            "^" (regexp-opt
+                                 (cl-loop for path
+                                          in (cdr (doom-module-load-path (list doom-modules-dir)))
+                                          for (_category . module)
+                                          = (doom-module-from-path path)
+                                          collect (symbol-name module))) "$")
+                           '("^&" "^cli$"))
+                     "\\|")
+                    (match-string 1)))))
+              "Invalid scope")
+
+        (cons (lambda ()
+                (when (looking-at "[^ :!(]+![(:]")
+                  (not (re-search-forward "^BREAKING CHANGE: .+" nil t))))
+              "'!' present in type, but missing 'BREAKING CHANGE:' in body")
+
+        (cons (lambda ()
+                (when (looking-at "[^ :!]+\\(([^)])\\)?: ")
+                  (re-search-forward "^BREAKING CHANGE: .+" nil t)))
+              "'BREAKING CHANGE:' present in body, but missing '!' in type")
+
+        (cons (lambda ()
+                (when (re-search-forward "^BREAKING CHANGE:" nil t)
+                  (not (looking-at " [^\n]+"))))
+              "'BREAKING CHANGE:' present in body, but empty")
+
+        (cons (lambda ()
+                (when (looking-at "bump: ")
+                  (let ((bump-re "^\\(https?://.+\\|[^/]+\\)/[^/]+@[a-z0-9]\\{7\\}"))
+                    (re-search-forward (concat "^" bump-re " -> " bump-re "$")
+                                       nil t))))
+              "Bump commit doesn't contain commit diff")
+
+        (cons (lambda ()
+                (re-search-forward "^\\(\\(Fix\\|Clos\\|Revert\\)ed\\|Reference[sd]\\): "
+                                   nil t))
+              "Use present tense/imperative voice for references, without a colon")
+
+        ;; TODO Check that bump/revert SUMMARY list: 1) valid modules and 2)
+        ;;      modules whose files are actually being touched.
+
+        ;; TODO Ensure your diff corraborates your SCOPE
+        ))
+
+(defun doom-cli--ci-hook-commit-msg (file)
+  (with-temp-buffer
+    (insert-file-contents file)
+    (let (errors)
+      (dolist (rule doom-cli-commit-rules)
+        (cl-destructuring-bind (pred . msg) rule
+          (goto-char (point-min))
+          (save-match-data
+            (when (if (functionp pred)
+                      (funcall pred)
+                    (if (stringp pred)
+                        (not (re-search-forward pred nil t))
+                      (error "Invalid predicate: %S" pred)))
+              (push msg errors)))))
+      (when errors
+        (print! (error "Your commit message failed to pass Doom's conventions, here's why:"))
+        (dolist (error (reverse errors))
+          (print-group! (print! (info error))))
+        (terpri)
+        (print! "See https://doomemacs.org/project.org#commit-message-formatting for details")
+        (throw 'exit 0))
+      t)))
+
+
+;;
+;;;
+
+(defun doom-cli--ci-lint-commits (from &optional to)
+  (with-temp-buffer
+    (save-excursion
+      (insert
+       (cdr (doom-call-process
+             "git" "log"
+             (format "%s...%s" from (or to "HEAD"))))))
+    (while (re-search-forward "^commit \\([a-z0-9]\\{40\\}\\)" nil t)
+      (let ((commit (match-string 1))
+            errors)
+        (forward-line 4)
+        (save-restriction
+          (save-match-data
+            (narrow-to-region
+             (point) (save-excursion
+                       (if (re-search-forward "^commit \\([a-z0-9]\\{40\\}\\)" nil t)
+                           (match-beginning 0)
+                         (point-max))))
+            (indent-rigidly (point-min) (point-max) -4))
+          (save-excursion
+            (print! (start "Commit %s") commit)
+            (dolist (rule doom-cli-commit-rules)
+              (cl-destructuring-bind (pred . msg) rule
+                (goto-char (point-min))
+                (save-match-data
+                  (when (if (functionp pred)
+                            (funcall pred)
+                          (if (stringp pred)
+                              (not (re-search-forward pred nil t))
+                            (error "Invalid predicate: %S" pred)))
+                    (push msg (alist-get commit errors nil nil #'equal)))))))
+          (when errors
+            (dolist (error (reverse errors))
+              (print! (error "Commit %s") (car error))
+              (print-group!
+               (dolist (e (reverse (cdr error)))
+                 (print! (info e)))))
+            (terpri)
+            (print! "%d commit(s) failed the linter" (length errors))
+            (terpri)
+            (print! "See https://doomemacs.org/project.org#commit-message-formatting for details")
+            (throw 'exit 1)))))
+    t))