On Fri, Mar 29, 2013 at 01:20:50PM -0700, Junio C Hamano wrote:
> John Keeping <john@xxxxxxxxxxxxx> writes:
>
> > After running the user's diff tool, git-difftool will copy any files
> > that differ between the working tree and the temporary tree. This is
> > useful when the user edits the file in their diff tool but is wrong if
> > they edit the working tree file while examining the diff.
>
> Thanks.
>
> I should drop the t7800-modernize topic and queue this under a
> better name. Perhaps "difftool-no-overwrite-on-copyback", or
> something.
>
> > Instead of copying unconditionally when the files differ, create and
> > index from the working tree files and only copy the temporary file back
> > if it was modified and the working tree file was not. If both files
> > have been modified, print a warning and exit with an error.
> >
> > Note that we cannot use an existing index in git-difftool since those
> > contain the modified files that need to be checked out but here we are
> > looking at those files which are copied from the working tree and not
> > checked out. These are precisely the files which are not in the
> > existing indices.
>
>
> >
> > Signed-off-by: John Keeping <john@xxxxxxxxxxxxx>
> >
> > ---
> > Changes since v2:
> > - Set TMPDIR to $TRASH_DIRECTORY in the test where difftool fails
> >
> > git-difftool.perl | 73 +++++++++++++++++++++++++++++++++++++++++++----------
> > t/t7800-difftool.sh | 30 ++++++++++++++++++++++
> > 2 files changed, 89 insertions(+), 14 deletions(-)
> >
> > diff --git a/git-difftool.perl b/git-difftool.perl
> > index 663640d..844f619 100755
> > --- a/git-difftool.perl
> > +++ b/git-difftool.perl
> > @@ -13,9 +13,9 @@
> > use 5.008;
> > use strict;
> > use warnings;
> > +use Error qw(:try);
> > use File::Basename qw(dirname);
> > use File::Copy;
> > -use File::Compare;
> > use File::Find;
> > use File::stat;
> > use File::Path qw(mkpath rmtree);
> > @@ -88,14 +88,45 @@ sub use_wt_file
> > my ($repo, $workdir, $file, $sha1, $symlinks) = @_;
> > my $null_sha1 = '0' x 40;
> >
> > - if ($sha1 eq $null_sha1) {
> > - return 1;
> > - } elsif (not $symlinks) {
> > + if ($sha1 ne $null_sha1 and not $symlinks) {
> > return 0;
> > }
> >
> > my $wt_sha1 = $repo->command_oneline('hash-object', "$workdir/$file");
> > - return $sha1 eq $wt_sha1;
> > + my $use = ($sha1 eq $null_sha1) || ($sha1 eq $wt_sha1);
> > + return ($use, $wt_sha1);
> > +}
> > +
> > +sub changed_files
> > +{
> > + my ($repo_path, $index, $worktree) = @_;
> > + $ENV{GIT_INDEX_FILE} = $index;
> > + $ENV{GIT_WORK_TREE} = $worktree;
> > + my $must_unset_git_dir = 0;
> > + if (not defined($ENV{GIT_DIR})) {
> > + $must_unset_git_dir = 1;
> > + $ENV{GIT_DIR} = $repo_path;
> > + }
> > +
> > + my @refreshargs = qw/update-index --really-refresh -q --unmerged/;
> > + my @gitargs = qw/diff-files --name-only -z/;
> > + try {
> > + Git::command_oneline(@refreshargs);
> > + } catch Git::Error::Command with {};
> > +
> > + my $line = Git::command_oneline(@gitargs);
> > + my @files;
> > + if (defined $line) {
> > + @files = split('\0', $line);
> > + } else {
> > + @files = ();
> > + }
> > +
> > + delete($ENV{GIT_INDEX_FILE});
> > + delete($ENV{GIT_WORK_TREE});
> > + delete($ENV{GIT_DIR}) if ($must_unset_git_dir);
> > +
> > + return map { $_ => 1 } @files;
> > }
> >
> > sub setup_dir_diff
> > @@ -121,6 +152,7 @@ sub setup_dir_diff
> > my $null_sha1 = '0' x 40;
> > my $lindex = '';
> > my $rindex = '';
> > + my $wtindex = '';
> > my %submodule;
> > my %symlink;
> > my @working_tree = ();
> > @@ -174,8 +206,12 @@ EOF
> > }
> >
> > if ($rmode ne $null_mode) {
> > - if (use_wt_file($repo, $workdir, $dst_path, $rsha1, $symlinks)) {
> > - push(@working_tree, $dst_path);
> > + my ($use, $wt_sha1) = use_wt_file($repo, $workdir,
> > + $dst_path, $rsha1,
> > + $symlinks);
> > + if ($use) {
> > + push @working_tree, $dst_path;
> > + $wtindex .= "$rmode $wt_sha1\t$dst_path\0";
> > } else {
> > $rindex .= "$rmode $rsha1\t$dst_path\0";
> > }
> > @@ -218,6 +254,12 @@ EOF
> > $rc = system('git', 'checkout-index', '--all', "--prefix=$rdir/");
> > exit_cleanup($tmpdir, $rc) if $rc != 0;
> >
> > + $ENV{GIT_INDEX_FILE} = "$tmpdir/wtindex";
> > + ($inpipe, $ctx) =
> > + $repo->command_input_pipe(qw(update-index --info-only -z --index-info));
> > + print($inpipe $wtindex);
> > + $repo->command_close_pipe($inpipe, $ctx);
> > +
> > # If $GIT_DIR was explicitly set just for the update/checkout
> > # commands, then it should be unset before continuing.
> > delete($ENV{GIT_DIR}) if ($must_unset_git_dir);
> > @@ -390,19 +432,22 @@ sub dir_diff
> > # should be copied back to the working tree.
> > # Do not copy back files when symlinks are used and the
> > # external tool did not replace the original link with a file.
> > + my %wt_modified = changed_files($repo->repo_path(),
> > + "$tmpdir/wtindex", "$workdir");
> > + my %tmp_modified = changed_files($repo->repo_path(),
> > + "$tmpdir/wtindex", "$b");
>
> Do we need to run these two comparisons unconditionally?
>
> It appears to me that in a sane and safe setting (i.e. $symlinks is
> set and the "diff viewer" touches the file through the symbolic
> link) does not ever look at wt_modified/tmp_modified at all because
> the first check in the loop will always trigger.
>
> I wonder if it makes sense to populate these two hashes lazily so
> that the safe case does not have to pay the penalty at all.
Sounds sensible. I'll look into doing this.
> > for my $file (@worktree) {
> > next if $symlinks && -l "$b/$file";
> > next if ! -f "$b/$file";
> >
> > + if (exists $wt_modified{$file} and exists $tmp_modified{$file}) {
> > + my $errmsg = "warning: Both files modified: ";
> > + $errmsg .= "'$workdir/$file' and '$b/$file'.\n";
> > + $errmsg .= "warning: Working tree file has been left.\n";
> > + $errmsg .= "warning:\n";
> > warn $errmsg;
> > $error = 1;
> > + } elsif ($tmp_modified{$file}) {
>
> "exists" if only for consistency?
Not just for consistency - this will generate an uninitialized value
warning if the tmp version of the file hasn't been modified.
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