Jeff King wrote:
On Wed, Sep 02, 2009 at 06:27:15PM +0100, James Spencer wrote:
$ git diff-files
$ touch test
$ git diff-files
:100644 100644 9daeafb9864cf43055ae93beb0afd6c7d144bfa4
0000000000000000000000000000000000000000 M test
$ git diff
$ git diff-files
$
I don't understand why git diff-files reports a file is changed when
that file is touched nor why running git diff changes this to (what I
think is) the correct behaviour.
Git uses the stat information of a file to know whether what we have
cached in the index is up-to-date or not. So in the first diff-files, we
don't even have to look at the contents of "test"; we see that it hasn't
changed since the last time we looked at the contents, and that its
sha-1 matches what's in the index, so there is no diff.
By running "touch", you have changed the stat information, so we believe
there may be a difference. But we don't actually know what's _in_ the
new side, so we just print the null sha1 instead of the actual sha1
contents.
Diff-files _could_ refresh the cache each time it runs, but we
intentionally do not do that. Doing so is a little bit expensive, and
because diff-files is intended as a low-level tool for scripts, we give
the script the flexibility (and responsibility) of refreshing the cache
when it wants to. So you could do:
$ git update-index --refresh
$ git diff-files
and get clean output.
You see different behavior from "git diff" because it is meant for user
consumption and therefore refreshes the cache automatically at the
beginning of every run.
-Peff
Thanks for your help!
--James
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