Improved ChangeLog generation for vc log (Bug#16301)

* lisp/vc/diff-mode.el (diff-find-source-location): Fix docstring.

* lisp/vc/add-log.el (change-log-unindented-file-names-re)
(change-log-read-entries, change-log-read-defuns)
(change-log-insert-entries):
* lisp/vc/diff-mode.el (diff-add-log-current-defuns):
* lisp/vc/log-edit.el (log-edit--insert-filled-defuns)
(log-edit-fill-entry): New functions.
(log-edit-mode): Set `log-edit-fill-entry' as
`fill-paragraph-function'.
(log-edit-generate-changelog-from-diff): New command.
(log-edit-mode-map): Bind it to C-c C-w.
* doc/emacs/maintaining.texi (Types of Log File, Log Buffer):
* CONTRIBUTE: Document it.
* etc/NEWS: Announce it.
* test/lisp/vc/log-edit-tests.el (log-edit-fill-entry)
(log-edit-fill-entry-joining): New tests.

1 files changed, 113 insertions, 0 deletions

diff --git a/test/lisp/vc/log-edit-tests.el b/test/lisp/vc/log-edit-tests.el
new file mode 100644
index 00000000000..7d77eca87d2
--- /dev/null
+++ b/test/lisp/vc/log-edit-tests.el
@@ -0,0 +1,113 @@
+;;; log-edit-tests.el --- Unit tests for log-edit.el  -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2019 Free Software Foundation, Inc.
+
+;; This file is part of GNU Emacs.
+
+;; 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 <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Unit tests for lisp/vc/log-edit.el.
+
+;;; Code:
+
+(require 'log-edit)
+(require 'ert)
+
+(ert-deftest log-edit-fill-entry ()
+  (with-temp-buffer
+    (insert "\
+* dir/file.ext (fun1):
+\(fun2):
+\(fun3):
+* file2.txt (fun4):
+\(fun5):
+\(fun6):
+\(fun7): Some prose.
+\(fun8): A longer description of a complicated change.\
+  Spread over a couple of sentencences.\
+  Long enough to be filled for several lines.
+\(fun9): Etc.")
+    (goto-char (point-min))
+    (let ((fill-column 72)) (log-edit-fill-entry))
+    (should (equal (buffer-string) "\
+* dir/file.ext (fun1, fun2, fun3):
+* file2.txt (fun4, fun5, fun6, fun7): Some prose.
+\(fun8): A longer description of a complicated change.  Spread over a
+couple of sentencences.  Long enough to be filled for several lines.
+\(fun9): Etc."))
+    (let ((fill-column 20)) (log-edit-fill-entry))
+    (should (equal (buffer-string) "\
+* dir/file.ext (fun1)
+\(fun2, fun3):
+* file2.txt (fun4)
+\(fun5, fun6, fun7):
+Some prose.
+\(fun8): A longer
+description of a
+complicated change.
+Spread over a couple
+of sentencences.
+Long enough to be
+filled for several
+lines.
+\(fun9): Etc."))
+    (let ((fill-column 40)) (log-edit-fill-entry))
+    (should (equal (buffer-string) "\
+* dir/file.ext (fun1, fun2, fun3):
+* file2.txt (fun4, fun5, fun6, fun7):
+Some prose.
+\(fun8): A longer description of a
+complicated change.  Spread over a
+couple of sentencences.  Long enough to
+be filled for several lines.
+\(fun9): Etc."))))
+
+(ert-deftest log-edit-fill-entry-trailing-prose ()
+  (with-temp-buffer
+    (insert "\
+* dir/file.ext (fun1): A longer description of a complicated change.\
+  Spread over a couple of sentencences.\
+  Long enough to be filled for several lines.")
+    (let ((fill-column 72)) (log-edit-fill-entry))
+    (should (equal (buffer-string) "\
+* dir/file.ext (fun1): A longer description of a complicated change.
+Spread over a couple of sentencences.  Long enough to be filled for
+several lines."))))
+
+(ert-deftest log-edit-fill-entry-joining ()
+  ;; Join short enough function names on the same line.
+  (with-temp-buffer
+    (insert "* dir/file.ext (fun1):\n(fun2):")
+    (let ((fill-column 72)) (log-edit-fill-entry))
+    (should (equal (buffer-string) "* dir/file.ext (fun1, fun2):")))
+  ;; Don't combine them if they're too long.
+  (with-temp-buffer
+    (insert "* dir/long-file-name.ext (a-really-long-function-name):
+\(another-very-long-function-name):")
+    (let ((fill-column 72)) (log-edit-fill-entry))
+    (should (equal (buffer-string) "* dir/long-file-name.ext (a-really-long-function-name)
+\(another-very-long-function-name):")))
+  ;; Put function name on next line, if the file name is too long.
+  (with-temp-buffer
+    (insert "\
+* a-very-long-directory-name/another-long-directory-name/and-a-long-file-name.ext\
+ (a-really-long-function-name):")
+    (let ((fill-column 72)) (log-edit-fill-entry))
+    (should (equal (buffer-string) "\
+* a-very-long-directory-name/another-long-directory-name/and-a-long-file-name.ext
+\(a-really-long-function-name):"))))
+
+;;; log-edit-tests.el ends here