Instead of running 'grep', 'echo', and 'wc' we simply compare
git-difftool's output against a known good value.
Signed-off-by: NDavid Aguilar <davvid@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

git-difftool requires difftool.<tool>.cmd configuration even when
tools use the standard "$diffcmd $from $to" form.  This teaches
git-difftool to run these tools in lieu of configuration by
allowing the command to be specified on the command line.

Reference: http://article.gmane.org/gmane.comp.version-control.git/133377Signed-off-by: NDavid Aguilar <davvid@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

An undocumented mis-feature in git-difftool is that it allows you
to specify a default difftool by setting GIT_MERGE_TOOL.
This behavior was never documented and was included as an
oversight back when git-difftool was maintained outside of git.

git-mergetool never honored GIT_MERGE_TOOL so neither should
git-difftool.
Signed-off-by: NDavid Aguilar <davvid@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Users might prefer to have git-difftool use a different
tool when run from a Git GUI.

This teaches git-difftool to honor 'diff.guitool' when
the '--gui' option is specified.  This allows users to
configure their preferred command-line diff tool in
'diff.tool' and a GUI diff tool in 'diff.guitool'.

Reference: http://article.gmane.org/gmane.comp.version-control.git/133386Signed-off-by: NDavid Aguilar <davvid@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

If a difftool test has an error then running the git test suite
may end up invoking a GUI diff tool.  We now guard against this
by setting a difftool.bogus-tool.cmd variable.

The tests already used --tool=bogus-tool in various places so
this is simply ensuring that nothing ever falls back and
finds a real diff tool.
Signed-off-by: NDavid Aguilar <davvid@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

GIT_DIFFTOOL_PROMPT doesn't have any effect if overridden with --prompt.
Signed-off-by: NMarkus Heidelberg <markus.heidelberg@web.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Difftool is written in perl, so we don't build it if NO_PERL
is set.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

difftool now supports difftool.prompt so that users do not have to
pass --no-prompt or hit enter each time a diff tool is launched.
The --prompt flag overrides the configuration variable.
Signed-off-by: NDavid Aguilar <davvid@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

t7800-difftool.sh tests the various command-line flags,
git-config variables, and environment settings supported by
git-difftool.
Signed-off-by: NDavid Aguilar <davvid@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>