git-diff: resurrect the traditional empty "diff --git" behaviour
The warning message to suggest "Consider running git-status" from
"git-diff" that we experimented with during the 1.5.3 cycle turns
out to be a bad idea. It robbed cache-dirty information from people
who valued it, while still asking users to run "update-index --refresh".
It was hoped that the new behaviour would at least have some educational
value, but not showing the cache-dirty paths like before meant that the
user would not even know easily which paths were cache-dirty, and it
made the need to refresh the index look like even more unnecessary chore.
This commit reinstates the traditional behaviour, but with a twist.
By default, the empty "diff --git" output is totally squelched out
from "git diff" output. At the end of the command, it automatically
runs "update-index --refresh" as needed, without even bothering the
user. In other words, people who do not care about the cache-dirtyness
do not even have to see the warning.
The traditional behaviour to see the stat-dirty output and to bypassing
the overhead of content comparison can be specified by setting the
configuration variable diff.autorefreshindex to false.
Signed-off-by: Junio C Hamano <firstname.lastname@example.org>