Emacs: Is there a way to generate a skeleton ChangeLog from diff?

Question

I'd like to partly automate creation of GNU-style ChangeLog entries when working with source code in version control. The add-changelog-entry-other-window works with one file at a time and you have to visit the file to use it.

What I'd like to see instead is to have some command that would take an output of diff -u -p (or have integration with VC modes so it could process svn diff etc) and to create all the skeleton entries at once.

For example, if svn status shows

D file1.c
M file2.c
A file3.c

the command would create

2009-09-05  My Name <my.email>

      * file1.c: Removed.
      * file2.c: WRITE YOUR CHANGES HERE
      * file3.c: New.

Better yet, if it could parse the changed files in some languages to an extent so it could offer:

  * file2.c (new_function): New function.
  (deleted_function): Removed.
  (changed_function): WRITE YOUR CHANGES HERE

I have found this feature in Emacs manual, but I don't see how I could apply it here.

Any suggestions? Thanks.

EDIT: One answer suggested vc-update-change-log. Unfortunately it only supports CVS and it creates ChangeLog entries by querying the already-commited VC logs. Thus even if it supported svn and others, it would be impossible to commit the changes and the ChangeLog in the same commit.

EDIT2: Apparently add-changelog-entry-other-window (C-x 4 a) works not only from visited file but from diff hunk involving that file too. (Source) This is almost what I am looking for. This together with elisp loop to iterate through all hunks should solve it.

Answer 1

There is a function vc-update-change-log that automatically generates change log entries from the version control log entries.

Answer 2

diff-add-change-log-entries-other-window is documented to do exactly what you mentioned in EDIT2:

diff-add-change-log-entries-other-window is an interactive compiled
Lisp function in `diff-mode.el'.

(diff-add-change-log-entries-other-window)

Iterate through the current diff and create ChangeLog entries.
I.e. like `add-change-log-entry-other-window' but applied to all hunks.

Unfortunately, it doesn't work very well for, say, new files: it doesn't even include the filenames of such files in the skeletal changelog entry.

You might have better luck with gcc's mklog script, which you can get from http://gcc.gnu.org/viewcvs/gcc/trunk/contrib/mklog.

Answer 3

I don't know of a function that does this, but it should be easy to implement. Basically, you want to

• get the changed files
• for each file, call add-change-log

"Find change log file, and add an entry for today and an item for this file.
Optional arg WHOAMI (interactive prefix) non-nil means prompt for user
name and email (stored in `add-log-full-name' and `add-log-mailing-address').

Second arg FILE-NAME is file name of the change log.
If nil, use the value of `change-log-default-name'.

Third arg OTHER-WINDOW non-nil means visit in other window.

Fourth arg NEW-ENTRY non-nil means always create a new entry at the front;
never append to an existing entry.  Option `add-log-keep-changes-together'
otherwise affects whether a new entry is created.

Option `add-log-always-start-new-record' non-nil means always create a
new record, even when the last record was made on the same date and by
the same person.

The change log file can start with a copyright notice and a copying
permission notice.  The first blank line indicates the end of these
notices.

Today's date is calculated according to `add-log-time-zone-rule' if
non-nil, otherwise in local time."

so the magic code is going to look something like

(apply 'make-magic-change-log-entry changed-files-list)

and make-magic-change-log-entry simply curries the add-change-log function so that the only argument is file-name — you set the other ones.