Re: "git diff-files" command reports differences that don't exist

[Junio C Hamano <gitster@pobox.com>]

Michael Brown <michael.brown@discourse.org> writes:

> What did you do before the bug happened? (Steps to reproduce your issue)
>
> 1. Be in any existing repository in a clean state (I tested with 2 existing
>    repositories and 1 completely fresh)
> 1. run `git diff-files`, see no output
> 1. touch an existing file: `touch a`
> 1. run `git diff-files`

This is totally expected behaviour.  In general when you are working
with plumbing commands like diff-files and diff-index, you are
expected to do "update-index --refresh" upfront.

A plumbing command "git diff" has an equivalent of "update-index
--refresh" built into it, but the plumbing commands are designed
to be used in scripts, and in order to allow scripting programmers
to avoid making unnecessary "update-index --refresh", e.g.

	git update-index --refresh
	git diff-files | use diff-files output
	git diff-index | use diff-index output

they leave it the responsibility of the calling script (or the end
user who directly use them from the command line) to refresh the
cached stat information as necessary.