Re: [PATCH 2/5] difftool: don't overwrite modified files
John Keeping <john@keeping.me.uk> 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.
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> 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.
Show 120 quoted lines
>
> Signed-off-by: John Keeping <john@keeping.me.uk>
>
> ---
> 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.
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> 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?
John Keeping