admin: Add gitmerge.el

* gitmerge.el: New file.

2 files changed, 532 insertions, 0 deletions

diff --git a/admin/ChangeLog b/admin/ChangeLog
index 6d134046a38..c30e4bea5b6 100644
--- a/admin/ChangeLog
+++ b/admin/ChangeLog
@@ -1,3 +1,7 @@
+2014-11-27  David Engster  <deng@randomsample.de>
+
+        * gitmerge.el: New file.
+
 2014-11-17  Oscar Fuentes  <ofv@wanadoo.es>
 
         * admin/CPP-DEFINES: Mention MINGW_W64.
diff --git a/admin/gitmerge.el b/admin/gitmerge.el
new file mode 100644
index 00000000000..88c633393a6
--- /dev/null
+++ b/admin/gitmerge.el
@@ -0,0 +1,528 @@
+;;; gitmerge.el --- help merge one Emacs branch into another
+
+;; Copyright (C) 2010-2014 Free Software Foundation, Inc.
+
+;; Authors: David Engster <deng@randomsample.de>
+;;          Stefan Monnier <monnier@iro.umontreal.ca>
+
+;; Keywords: maint
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Rewrite of bzrmerge.el, but using git.
+;;
+;; In a nutshell: For merging foo into master, do
+;;
+;; - 'git checkout master' in Emacs repository
+;; - Start Emacs, cd to Emacs repository
+;; - M-x gitmerge
+;; - Choose branch 'foo' or 'origin/foo', depending on whether you
+;;   like to merge from a local tracking branch or from the remote
+;;   (does not make a difference if the local tracking branch is
+;;   up-to-date).
+;; - Mark commits you'd like to skip, meaning to only merge their
+;;   metadata (merge strategy 'ours').
+;; - Hit 'm' to start merging. Skipped commits will be merged separately.
+;; - If conflicts cannot be resolved automatically, you'll have to do
+;;   it manually. In that case, resolve the conflicts and restart
+;;   gitmerge, which will automatically resume. It will add resolved
+;;   files, commit the pending merge and continue merging the rest.
+;; - Inspect master branch, and if everything looks OK, push.
+
+;;; Code:
+
+(require 'vc-git)
+(require 'smerge-mode)
+
+(defvar gitmerge-skip-regexp
+  "back[- ]?port\\|merge\\|sync\\|re-?generate\\|bump version\\|from trunk\\|\
+Auto-commit"
+  "Regexp matching logs of revisions that might be skipped.
+`gitmerge-missing' will ask you if it should skip any matches.")
+
+(defvar gitmerge-status-file (expand-file-name "gitmerge-status"
+                                               user-emacs-directory)
+  "File where missing commits will be saved between sessions.")
+
+(defvar gitmerge-ignore-branches-regexp
+  "origin/\\(\\(HEAD\\|master\\)$\\|\\(old-branches\\|other-branches\\)/\\)"
+  "Regexp matching branches we want to ignore.")
+
+(defface gitmerge-skip-face
+  '((t (:strike-through t)))
+  "Face for skipped commits.")
+
+(defconst gitmerge-default-branch "origin/emacs-24"
+  "Default for branch that should be merged.")
+
+(defconst gitmerge-buffer "*gitmerge*"
+  "Working buffer for gitmerge.")
+
+(defconst gitmerge-output-buffer "*gitmerge output*"
+  "Buffer for displaying git output.")
+
+(defconst gitmerge-warning-buffer "*gitmerge warnings*"
+  "Buffer where gitmerge will display any warnings.")
+
+(defvar gitmerge-log-regexp
+  "^\\([A-Z ]\\)\\s-*\\([0-9a-f]+\\) \\(.+?\\): \\(.*\\)$")
+
+(defvar gitmerge-mode-map
+  (let ((map (make-keymap)))
+    (define-key map [(l)] 'gitmerge-show-log)
+    (define-key map [(d)] 'gitmerge-show-diff)
+    (define-key map [(f)] 'gitmerge-show-files)
+    (define-key map [(s)] 'gitmerge-toggle-skip)
+    (define-key map [(m)] 'gitmerge-start-merge)
+    map)
+  "Keymap for gitmerge major mode.")
+
+(defvar gitmerge--commits nil)
+(defvar gitmerge--from nil)
+
+(defun gitmerge-get-sha1 ()
+  "Get SHA1 from commit at point."
+  (save-excursion
+    (goto-char (point-at-bol))
+    (when (looking-at "^[A-Z ]\\s-*\\([a-f0-9]+\\)")
+      (match-string 1))))
+
+(defun gitmerge-show-log ()
+  "Show log of commit at point."
+  (interactive)
+  (save-selected-window
+    (let ((commit (gitmerge-get-sha1)))
+      (when commit
+        (pop-to-buffer (get-buffer-create gitmerge-output-buffer))
+        (fundamental-mode)
+        (erase-buffer)
+        (call-process "git" nil t nil "log" "-1" commit)
+        (goto-char (point-min))
+        (gitmerge-highlight-skip-regexp)))))
+
+(defun gitmerge-show-diff ()
+  "Show diff of commit at point."
+  (interactive)
+  (save-selected-window
+    (let ((commit (gitmerge-get-sha1)))
+      (when commit
+        (pop-to-buffer (get-buffer-create gitmerge-output-buffer))
+        (erase-buffer)
+        (call-process "git" nil t nil "diff-tree" "-p" commit)
+        (goto-char (point-min))
+        (diff-mode)))))
+
+(defun gitmerge-show-files ()
+  "Show changed files of commit at point."
+  (interactive)
+  (save-selected-window
+    (let ((commit (gitmerge-get-sha1)))
+      (when commit
+        (pop-to-buffer (get-buffer-create gitmerge-output-buffer))
+        (erase-buffer)
+        (fundamental-mode)
+        (call-process "git" nil t nil "diff" "--name-only" (concat commit "^!"))
+        (goto-char (point-min))))))
+
+(defun gitmerge-toggle-skip ()
+  "Toggle skipping of commit at point."
+  (interactive)
+  (let ((commit (gitmerge-get-sha1))
+        skip)
+    (when commit
+      (save-excursion
+        (goto-char (point-at-bol))
+        (when (looking-at "^\\([A-Z ]\\)\\s-*\\([a-f0-9]+\\)")
+          (setq skip (string= (match-string 1) " "))
+          (goto-char (match-beginning 2))
+          (gitmerge-handle-skip-overlay skip)
+          (dolist (ct gitmerge--commits)
+            (when (string-match commit (car ct))
+              (setcdr ct (when skip "M"))))
+          (goto-char (point-at-bol))
+          (setq buffer-read-only nil)
+          (delete-char 1)
+          (insert (if skip "M" " "))
+          (setq buffer-read-only t))))))
+          
+(defun gitmerge-highlight-skip-regexp ()
+  "Highlight strings that match `gitmerge-skip-regexp'."
+  (save-excursion
+    (while (re-search-forward gitmerge-skip-regexp nil t)
+      (put-text-property (match-beginning 0) (match-end 0)
+                         'face 'font-lock-warning-face))))
+
+(defun gitmerge-missing (from)
+  "Return the list of revisions that need to be merged from FROM.
+Will detect a default set of skipped revision by looking at
+cherry mark and search for `gitmerge-skip-regexp'.  The result is
+a list with entries of the form (SHA1 . SKIP), where SKIP denotes
+if and why this commit should be skipped."
+  (let (commits)
+    ;; Go through the log and remember all commits that match
+    ;; `gitmerge-skip-regexp' or are marked by --cherry-mark.
+    (with-temp-buffer
+      (call-process "git" nil t nil "log" "--cherry-mark" from
+                    (concat "^" (car (vc-git-branches))))
+      (goto-char (point-max))
+      (while (re-search-backward "^commit \\(.+\\) \\([0-9a-f]+\\).*" nil t)
+        (let ((cherrymark (match-string 1))
+              (commit (match-string 2)))
+          (push (list commit) commits)
+          (if (string= cherrymark "=")
+              ;; Commit was recognized as backported by cherry-mark.
+              (setcdr (car commits) "C")
+            (save-excursion
+              (let ((case-fold-search t))
+                (while (not (looking-at "^\\s-+[^ ]+"))
+                  (forward-line))
+                (when (re-search-forward gitmerge-skip-regexp nil t)
+                  (setcdr (car commits) "R"))))))
+        (delete-region (point) (point-max))))
+    (nreverse commits)))
+
+(defun gitmerge-setup-log-buffer (commits from)
+  "Create the buffer for choosing commits."
+  (with-current-buffer (get-buffer-create gitmerge-buffer)
+    (erase-buffer)
+    (call-process "git" nil t nil "log"
+                  "--pretty=format:%h %<(20,trunc) %an: %<(100,trunc) %s"
+                  from (concat "^" (car (vc-git-branches))))
+    (goto-char (point-min))
+    (while (looking-at "^\\([a-f0-9]+\\)")
+      (let ((skipreason (gitmerge-skip-commit-p (match-string 1) commits)))
+        (if (null skipreason)
+            (insert "  ")
+          (insert skipreason " ")
+          (gitmerge-handle-skip-overlay t)))
+      (forward-line))
+    (current-buffer)))
+
+(defun gitmerge-handle-skip-overlay (skip)
+  "Create or delete overlay on SHA1, depending on SKIP."
+  (when (looking-at "[0-9a-f]+")
+    (if skip
+        (let ((ov (make-overlay (point)
+                                (match-end 0))))
+          (overlay-put ov 'face 'gitmerge-skip-face))
+      (remove-overlays (point) (match-end 0)
+                       'face 'gitmerge-skip-face))))
+
+(defun gitmerge-skip-commit-p (commit skips)
+  "Tell whether COMMIT should be skipped.
+COMMIT is an (possibly abbreviated) SHA1.  SKIPS is list of
+cons'es with commits that should be skipped and the reason.
+Return value is string which denotes reason, or nil if commit
+should not be skipped."
+  (let (found skip)
+    (while (and (setq skip (pop skips))
+                (not found))
+      (when (string-match commit (car skip))
+        (setq found (cdr skip))))
+    found))
+
+(defun gitmerge-resolve (file)
+  "Try to resolve conflicts in FILE with smerge.
+Returns non-nil if conflicts remain."
+  (unless (file-exists-p file) (error "Gitmerge-resolve: Can't find %s" file))
+  (with-demoted-errors
+    (let ((exists (find-buffer-visiting file)))
+      (with-current-buffer (let ((enable-local-variables :safe)
+                                 (enable-local-eval nil))
+                             (find-file-noselect file))
+        (if (buffer-modified-p)
+            (user-error "Unsaved changes in %s" (current-buffer)))
+        (save-excursion
+          (cond
+           ((derived-mode-p 'change-log-mode)
+            ;; Fix up dates before resolving the conflicts.
+            (goto-char (point-min))
+            (let ((diff-auto-refine-mode nil))
+              (while (re-search-forward smerge-begin-re nil t)
+                (smerge-match-conflict)
+                (smerge-ensure-match 3)
+                (let ((start1 (match-beginning 1))
+                      (end1 (match-end 1))
+                      (start3 (match-beginning 3))
+                      (end3 (copy-marker (match-end 3) t)))
+                  (goto-char start3)
+                  (while (re-search-forward change-log-start-entry-re end3 t)
+                    (let* ((str (match-string 0))
+                           (newstr (save-match-data
+                                     (concat (add-log-iso8601-time-string)
+                                             (when (string-match " *\\'" str)
+                                               (match-string 0 str))))))
+                      (replace-match newstr t t)))
+                  ;; change-log-resolve-conflict prefers to put match-1's
+                  ;; elements first (for equal dates), whereas we want to put
+                  ;; match-3's first.
+                  (let ((match3 (buffer-substring start3 end3))
+                        (match1 (buffer-substring start1 end1)))
+                    (delete-region start3 end3)
+                    (goto-char start3)
+                    (insert match1)
+                    (delete-region start1 end1)
+                    (goto-char start1)
+                    (insert match3)))))
+            ;; (pop-to-buffer (current-buffer)) (debug 'before-resolve)
+            ))
+          ;; Try to resolve the conflicts.
+          (cond
+           ((member file '("configure" "lisp/ldefs-boot.el"
+                           "lisp/emacs-lisp/cl-loaddefs.el"))
+            ;; We are in the file's buffer, so names are relative.
+            (call-process "git" nil t nil "checkout" "--"
+                          (file-name-nondirectory file))
+            (revert-buffer nil 'noconfirm))
+           (t
+            (goto-char (point-max))
+            (while (re-search-backward smerge-begin-re nil t)
+              (save-excursion
+                (ignore-errors
+                  (smerge-match-conflict)
+                  (smerge-resolve))))
+            ;; (when (derived-mode-p 'change-log-mode)
+            ;;   (pop-to-buffer (current-buffer)) (debug 'after-resolve))
+            (save-buffer)))
+          (goto-char (point-min))
+          (prog1 (re-search-forward smerge-begin-re nil t)
+            (unless exists (kill-buffer))))))))
+
+(defun gitmerge-commit-message (beg end skip branch)
+  "Create commit message for merging BEG to END from BRANCH.
+SKIP denotes whether those commits are actually skipped.  If END
+is nil, only the single commit BEG is merged."
+  (with-temp-buffer
+    (insert "Merge from " branch "\n\n"
+            (if skip
+                (concat "The following commit"
+                        (if end "s were " " was ")
+                        "skipped:\n\n")
+              ""))
+    (apply 'call-process "git" nil t nil "log" "--oneline"
+           (if end (list (concat beg "~.." end))
+             `("-1" ,beg)))
+    (insert "\n")
+    (buffer-string)))
+
+(defun gitmerge-apply (missing from)
+  "Merge commits in MISSING from branch FROM.
+MISSING must be a list of SHA1 strings."
+  (with-current-buffer (get-buffer-create gitmerge-output-buffer)
+    (erase-buffer)
+    (let* ((skip (cdar missing))
+           (beg (car (pop missing)))
+           end commitmessage)
+      ;; Determine last revision with same boolean skip status.
+      (while (and missing
+                  (eq (null (cdar missing))
+                      (null skip)))
+        (setq end (car (pop missing))))
+      (setq commitmessage
+            (gitmerge-commit-message beg end skip from))
+      (message "%s %s%s"
+               (if skip "Skipping" "Merging")
+               (substring beg 0 6)
+               (if end (concat ".." (substring end 0 6)) ""))
+      (unless end
+        (setq end beg))
+      (unless (zerop
+               (apply 'call-process "git" nil t nil "merge" "--no-ff"
+                      (append (when skip '("-s" "ours"))
+                              `("-m" ,commitmessage ,end))))
+        (gitmerge-write-missing missing from)
+        (gitmerge-resolve-unmerged)))
+    missing))
+
+(defun gitmerge-resolve-unmerged ()
+  "Resolve all files that are unmerged.
+Throw an user-error if we cannot resolve automatically."
+  (with-current-buffer (get-buffer-create gitmerge-output-buffer)
+    (erase-buffer)
+    (let (files conflicted)
+      ;; List unmerged files
+      (if (not (zerop
+                (call-process "git" nil t nil
+                              "diff" "--name-only" "--diff-filter=U")))
+          (error "Error listing unmerged files. Resolve manually.")
+        (goto-char (point-min))
+        (while (not (eobp))
+          (push (buffer-substring (point) (line-end-position)) files)
+          (forward-line))      
+        (dolist (file files)
+          (if (gitmerge-resolve file)
+              ;; File still has conflicts
+              (setq conflicted t)
+            ;; Mark as resolved
+            (call-process "git" nil t nil "add" file)))
+        (when conflicted
+          (with-current-buffer (get-buffer-create gitmerge-warning-buffer)
+            (erase-buffer)
+            (insert "For the following files, conflicts could\n"
+                    "not be resolved automatically:\n\n")
+            (call-process "git" nil t nil
+                          "diff" "--name-only" "--diff-filter=U")
+            (insert "\nResolve the conflicts manually, then run gitmerge again."
+                    "\nNote:\n  - You don't have to add resolved files or "
+                    "commit the merge yourself (but you can)."
+                    "\n  - You can safely close this Emacs session and do this "
+                    "in a new one."
+                    "\n  - When running gitmerge again, remember that you must "
+                    "that from within the Emacs repo.\n")
+            (pop-to-buffer (current-buffer)))
+          (user-error "Resolve the conflicts manually"))))))
+
+(defun gitmerge-repo-clean ()
+  "Return non-nil if repository is clean."
+  (with-temp-buffer
+      (call-process "git" nil t nil
+                    "diff" "--staged" "--name-only")
+      (call-process "git" nil t nil
+                    "diff" "--name-only")
+      (zerop (buffer-size))))
+  
+(defun gitmerge-maybe-resume ()
+  "Check if we have to resume a merge.
+If so, add no longer conflicted files and commit."
+  (let ((mergehead (file-exists-p
+                    (expand-file-name ".git/MERGE_HEAD" default-directory)))
+        (statusexist (file-exists-p gitmerge-status-file)))
+    (when (and mergehead (not statusexist))
+      (user-error "Unfinished merge, but no record of a previous gitmerge run"))
+    (when (and (not mergehead)
+               (not (gitmerge-repo-clean)))
+      (user-error "Repository is not clean"))
+    (when statusexist
+      (if (not (y-or-n-p "Resume merge? "))
+          (progn
+            (delete-file gitmerge-status-file)
+            ;; No resume.
+            nil)
+        (message "OK, resuming...")
+        (gitmerge-resolve-unmerged)
+        ;; Commit the merge.
+        (when mergehead
+          (with-current-buffer (get-buffer-create gitmerge-output-buffer)
+            (erase-buffer)
+            (unless (zerop (call-process "git" nil t nil
+                                         "commit" "--no-edit"))
+              (error "Git error during merge - fix it manually"))))
+        ;; Sucesfully resumed.
+        t))))
+
+(defun gitmerge-get-all-branches ()
+  "Return list of all branches, including remotes."
+  (with-temp-buffer
+    (unless (zerop (call-process "git" nil t nil
+                                 "branch" "-a"))
+      (error "Git error listing remote branches"))
+    (goto-char (point-min))
+    (let (branches branch)
+      (while (not (eobp))
+        (when (looking-at "^[^\\*]\\s-*\\(?:remotes/\\)?\\(.+\\)$")
+          (setq branch (match-string 1))
+          (unless (string-match gitmerge-ignore-branches-regexp branch)
+            (push branch branches)))
+        (forward-line))
+      (nreverse branches))))
+
+(defun gitmerge-write-missing (missing from)
+  "Write list of commits MISSING into `gitmerge-status-file'.
+Branch FROM will be prepended to the list."
+  (with-current-buffer
+      (find-file-noselect gitmerge-status-file)
+    (erase-buffer)
+    (insert
+     (prin1-to-string (append (list from) missing))
+     "\n")
+    (save-buffer)
+    (kill-buffer)))
+
+(defun gitmerge-read-missing ()
+  "Read list of missing commits from `gitmerge-status-file'."
+  (with-current-buffer
+      (find-file-noselect gitmerge-status-file)
+    (unless (zerop (buffer-size))
+      (prog1 (read (buffer-string))
+        (kill-buffer)))))
+
+(defun gitmerge-mode ()
+  "Major mode for Emacs branch merging."
+  (interactive)
+  (kill-all-local-variables)
+  (setq major-mode 'gitmerge-mode)
+  (setq mode-name "gitmerge")
+  (set-syntax-table text-mode-syntax-table)
+  (use-local-map gitmerge-mode-map)
+  (make-local-variable 'font-lock-defaults)
+  (setq gitmerge-mode-font-lock-keywords
+        (list (list gitmerge-log-regexp
+                    '(1 font-lock-warning-face)
+                    '(2 font-lock-constant-face)
+                    '(3 font-lock-builtin-face)
+                    '(4 font-lock-comment-face))))
+  (setq buffer-read-only t)
+  (setq font-lock-defaults '(gitmerge-mode-font-lock-keywords)))
+
+(defun gitmerge (from)
+  "Merge from branch FROM into `default-directory'."
+  (interactive
+   (if (not (vc-git-root default-directory))
+       (user-error "Not in a git tree")
+     (let ((default-directory (vc-git-root default-directory)))
+       (list
+        (if (gitmerge-maybe-resume)
+            'resume
+          (completing-read "Merge branch: " (gitmerge-get-all-branches)
+                           nil t gitmerge-default-branch))))))
+  (let ((default-directory (vc-git-root default-directory)))
+    (if (eq from 'resume)
+        (progn
+          (setq gitmerge--commits (gitmerge-read-missing))
+          (setq gitmerge--from (pop gitmerge--commits))
+          ;; Directly continue with the merge.
+          (gitmerge-start-merge))
+      (setq gitmerge--commits (gitmerge-missing from))
+      (setq gitmerge--from from)
+      (when (null gitmerge--commits)
+        (user-error "Nothing to merge"))
+      (with-current-buffer
+          (gitmerge-setup-log-buffer gitmerge--commits gitmerge--from)
+        (goto-char (point-min))
+        (insert (propertize "Commands: " 'font-lock-face 'bold)
+                "(s) Toggle skip, (l) Show log, (d) Show diff, "
+                "(f) Show files, (m) Start merge\n"
+                (propertize "Flags:    " 'font-lock-face 'bold)
+                "(C) Detected backport (cherry-mark), (R) Log matches "
+                "regexp, (M) Manually picked\n\n")
+        (gitmerge-mode)
+        (pop-to-buffer (current-buffer))))))
+
+(defun gitmerge-start-merge ()
+  (interactive)
+  (when (not (vc-git-root default-directory))
+    (user-error "Not in a git tree"))
+  (let ((default-directory (vc-git-root default-directory)))
+    (while gitmerge--commits
+      (setq gitmerge--commits
+            (gitmerge-apply gitmerge--commits gitmerge--from)))
+    (when (file-exists-p gitmerge-status-file)
+      (delete-file gitmerge-status-file))
+    (message "Merging from %s...done" gitmerge--from)))
+
+(provide 'gitmerge)
+
+;;; gitmerge.el ends here