Re: [PATCH v6] difftool.c: learn a new way start at specified file

>
> From: ZheNing Hu <adlternative@gmail.com>
>
> `git difftool` only allow us to select file to view in turn.
> If there is a commit with many files and we exit in the middle,
> we will have to traverse list again to get the file diff which
> we want to see. Therefore,teach the command an option
> `--skip-to=<path>` to allow the user to say that diffs for earlier
> paths are not interesting (because they were already seen in an
> earlier session) and start this session with the named path.
>
> Signed-off-by: ZheNing Hu <adlternative@gmail.com>
> ---
>     difftool.c: learn a new way start at specified file
>
>      * The patch of the previous version implemented the jump through
>        environment variables. The current version is based on the "diff
>        --skip-to=" feature implemented by gitster, which implements a
>        possible solution for the jump of difftool.
>
> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-870%2Fadlternative%2Fdifftool_save_point-v6
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-870/adlternative/difftool_save_point-v6
> Pull-Request: https://github.com/gitgitgadget/git/pull/870
>
> Range-diff vs v5:
>
>  1:  fb4bfd0f8b16 < -:  ------------ diff: --{rotate,skip}-to=<path>
>  2:  98e2707ee2fa ! 1:  4377a917ca9e difftool.c: learn a new way start at specified file
>      @@ Commit message
>           difftool.c: learn a new way start at specified file
>
>           `git difftool` only allow us to select file to view in turn.
>      -    If there is a commit with many files and we exit in the search,
>      -    We will have to traverse list again to get the file diff which
>      -    we want to see. Therefore, here is a new method: user can use
>      -    `git difftool --rotate-to=<filename>` or `git difftool --skip-to=<filename>`
>      -    to start viewing from the specified file, This will improve the
>      -    user experience.
>      -
>      -    `git difftool --rotate-to=<file>` or `git difftool --skip-to=<filename>`
>      -    will pass the path to `diffcore-rotate`, and diff-core will
>      -    adjust the order of files, make the specified file sorted to
>      -    the first.`git difftool --rotate-to=<file>` will move files before
>      -    the  specified path to the last output, and
>      -    `git difftool --skip-to=<filename>`  will ignore these files output.
>      -    It is an error when there is no patch for specified file is shown.
>      +    If there is a commit with many files and we exit in the middle,
>      +    we will have to traverse list again to get the file diff which
>      +    we want to see. Therefore,teach the command an option
>      +    `--skip-to=<path>` to allow the user to say that diffs for earlier
>      +    paths are not interesting (because they were already seen in an
>      +    earlier session) and start this session with the named path.
>
>           Signed-off-by: ZheNing Hu <adlternative@gmail.com>
>
>      - ## Documentation/diff-options.txt ##
>      -@@ Documentation/diff-options.txt: components matches the pattern.  For example, the pattern "`foo*bar`"
>      - matches "`fooasdfbar`" and "`foo/bar/baz/asdf`" but not "`foobarx`".
>      -
>      - --skip-to=<file>::
>      ----rotate-to=<file::
>      -+--rotate-to=<file>::
>      -  Discard the files before the named <file> from the output
>      -  (i.e. 'skip to'), or move them to the end of the output
>      -  (i.e. 'rotate to').  These were invented primarily for use
>      -
>        ## Documentation/git-difftool.txt ##
>       @@ Documentation/git-difftool.txt: OPTIONS
>         This is the default behaviour; the option is provided to
>         override any configuration settings.
>
>       +--rotate-to=<file>::
>      -+ Internally call `git diff --rotate-to=<file>`,
>      -+ show the change in the specified path first.
>      -+ Files before the specified path will be moved to the last output.
>      ++ Start showing the diff for the given path,
>      ++ the paths before it will move to end and output.
>       +
>       +--skip-to=<file>::
>      -+ Internally call `git diff --skip-to=<file>`,
>      -+ skip the output to the specified path.
>      -+ Files before the specified path will not output.
>      ++ Start showing the diff for the given path, skipping all
>      ++ the paths before it.
>       +
>        -t <tool>::
>        --tool=<tool>::
>      @@ t/t7800-difftool.sh: test_expect_success 'difftool --gui, --tool and --extcmd ar
>       + 4
>       + 1
>       + EOF
>      -+ test_cmp output expect &&
>      -+ test_must_fail git difftool --no-prompt --extcmd=cat --rotate-to="3" HEAD^
>      ++ test_cmp output expect
>       +'
>       +
>       +test_expect_success 'difftool --skip-to' '
>      @@ t/t7800-difftool.sh: test_expect_success 'difftool --gui, --tool and --extcmd ar
>       + 2
>       + 4
>       + EOF
>      -+ test_cmp output expect &&
>      -+ test_must_fail git difftool --no-prompt --extcmd=cat --skip-to="3" HEAD^
>      ++ test_cmp output expect
>       +'
>       +
>      ++test_expect_success 'difftool --rotate/skip-to error condition' '
>      ++ test_must_fail git difftool --no-prompt --extcmd=cat --rotate-to="3" HEAD^ &&
>      ++ test_must_fail git difftool --no-prompt --extcmd=cat --skip-to="3" HEAD^
>      ++'
>        test_done
>
>
>  Documentation/git-difftool.txt |  8 ++++++++
>  t/t7800-difftool.sh            | 32 ++++++++++++++++++++++++++++++++
>  2 files changed, 40 insertions(+)
>
> diff --git a/Documentation/git-difftool.txt b/Documentation/git-difftool.txt
> index 484c485fd06c..143b0c49d739 100644
> --- a/Documentation/git-difftool.txt
> +++ b/Documentation/git-difftool.txt
> @@ -34,6 +34,14 @@ OPTIONS
>         This is the default behaviour; the option is provided to
>         override any configuration settings.
>
> +--rotate-to=<file>::
> +       Start showing the diff for the given path,
> +       the paths before it will move to end and output.
> +
> +--skip-to=<file>::
> +       Start showing the diff for the given path, skipping all
> +       the paths before it.
> +
>  -t <tool>::
>  --tool=<tool>::
>         Use the diff tool specified by <tool>.  Valid values include
> diff --git a/t/t7800-difftool.sh b/t/t7800-difftool.sh
> index 9192c141ffc6..3e041e83aede 100755
> --- a/t/t7800-difftool.sh
> +++ b/t/t7800-difftool.sh
> @@ -762,4 +762,36 @@ test_expect_success 'difftool --gui, --tool and --extcmd are mutually exclusive'
>         test_must_fail git difftool --gui --tool=test-tool --extcmd=cat
>  '
>
> +test_expect_success 'difftool --rotate-to' '
> +       difftool_test_setup &&
> +       test_when_finished git reset --hard &&
> +       echo 1 >1 &&
> +       echo 2 >2 &&
> +       echo 4 >4 &&
> +       git add 1 2 4 &&
> +       git commit -a -m "124" &&
> +       git difftool --no-prompt --extcmd=cat --rotate-to="2" HEAD^ >output&&
> +       cat >expect <<-\EOF &&
> +       2
> +       4
> +       1
> +       EOF
> +       test_cmp output expect
> +'
> +
> +test_expect_success 'difftool --skip-to' '
> +       difftool_test_setup &&
> +       test_when_finished git reset --hard &&
> +       git difftool --no-prompt --extcmd=cat --skip-to="2" HEAD^ >output &&
> +       cat >expect <<-\EOF &&
> +       2
> +       4
> +       EOF
> +       test_cmp output expect
> +'
> +
> +test_expect_success 'difftool --rotate/skip-to error condition' '
> +       test_must_fail git difftool --no-prompt --extcmd=cat --rotate-to="3" HEAD^ &&
> +       test_must_fail git difftool --no-prompt --extcmd=cat --skip-to="3" HEAD^
> +'
>  test_done
>
> base-commit: 1eb4136ac2a24764257567b930535fcece01719f
> --
> gitgitgadget