Re: preserving mtime

From: Junio C Hamano <gitster@pobox.com>
Date: Nov 16, 2007, 10:21 UTC
Message-ID: <7v1waqze1b.fsf@gitster.siamese.dyndns.org>
In-Reply-To: <473D63F9.4010201@inrim.it>

Fabrizio Pollastri <f.pollastri@inrim.it> writes:

> is it possible to tell git to preserve the file modification time in a
> checked out copy? It is useful when managing web files, where mtime is
> tested by spiders for download decisions.

"git checkout branchA" after "git checkout branchB" would not touch "file" if "file" are identical between two branches, so the modification time is already preserved.

If the contents of "file" from the version you would want to check out is different from the version you previously checked out, and you still want to keep the old timestamp, then you are trying to do something that a normal SCM user would actively not want (e.g. doing so would screw up the build systems such as "make"). Such a specialized need usually is addressed by the build and install procedure of the application (in your case, a website management). Maybe your current build procedure may blindly copy when installing:

	install: web.html
        	$(install) web.html $(dest)/var/www/web.html

but you may want to ignore certain classes of changes and avoid re-installing to help crawlers. You would do:

	install = ./myinstall.sh
	install: web.html
        	$(install) web.html $(dest)/var/www/web.html

and then ./myinstall.sh might look like:

	#!/bin/sh
	test -f "$2" &&
        compare-ignoring-minor-changes "$1" "$2" && exit 0
	install "$1" "$2"