Untouch Extension

Save or restore modification times of files.

1. Status

This extension is not distributed with Mercurial.

Author: Michael Platings

Repository: http://bitbucket.org/mplatings/hg-untouch/

2. Overview

For users of languages such as C++ that can have long compilation times, a fairly major irritation of Mercurial is the following scenario:

• You make a change in a widely included header file.
• To ensure that you haven't broken anything, you run make and wait for an hour while everything rebuilds.
• There are no new build errors so you commit the change.

• Before you can push, you must hg pull --rebase or hg update and hg merge.

• Several new changesets are pulled so you run make again to make sure your change hasn't broken them.
• Except Mercurial has touched the header you changed so now you've got to wait for another hour while make runs, even though none of the changesets you pulled are related to the header.
• In that hour you waited for make to run again, more changesets have been added so now you're stuck in an infinite loop of pull and make.

The untouch extension remedies this problem by saving and restoring file modification times.

This extension can be used in 3 ways:

1. When running hg pull with the --rebase option and without any resulting conflicts. The extension will automatically restore file modified times without any user input.

   Example:

    hg pull --rebase

2. To explicitly save file modified times and later restore them.

   Running hg untouch --save will record the modified times of files in the working directory whose status is "added" or "modified" as well as files that are modified by ancestor changesets whose phase is "draft" or "secret".

   Running hg untouch will restore the modified times recorded by previously running hg untouch --save.

   Example:

    hg untouch --save
    hg update tip
    hg merge
    hg commit -m "merge"
    hg untouch

3. Any time after running hg pull

   The user may run hg untouch --prepull to restore the modified times of certain files. The files will be those that were modified by ancestor changesets whose phase was "draft" or "secret" at the time hg pull was run.

   The prepull modified times are independent of those created by hg untouch --save so hg untouch --prepull can be used independently of hg untouch.

   Example:

    hg pull
    hg update
    hg merge
    hg commit -m "merge"
    hg untouch --prepull

The extension will never change the modified time of a file if it finds that the file's content has changed since its modified time was recorded.

3. Configuration

Configure your .hgrc to enable the extension by adding following lines:

[extensions]
untouch = path/to/untouch.py
[hooks]
pre-pull.untouch = python:path/to/untouch.py:hook_pre_pull
post-pull.untouch = python:path/to/untouch.py:hook_post_pull

4. See also

• The qtimes extension is similar but focussed on files affected by patch queues only.

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