Re: [PATCH v2] git-difftool-helper.sh: learn a new way go back to last save point

>
> (cc'd Ryan since the thread involving him was mentioned in the commit message)
>
> On Mon, Feb 8, 2021 at 9:02 AM ZheNing Hu via GitGitGadget
> <gitgitgadget@gmail.com> wrote:
> >
> > 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 search,
> > We will have to traverse list again to get the file diff which
> > we want to see. Therefore, here is a new method: every time before
> > we view the file diff, the current coordinates will be stored in
> > `GIT_DIR/difftool-last-position`, this file will be deleted after
> > successful traversing. But if an unexpected exit occurred midway or
> > users similar to using "ctrl+c" kill the process,and the user wants
> > to redo the same `git difftoool`, git will view the coordinates in
> > the save point, ask user if they want continue from the last position.
> > This will improve the user experience.
> >
> > Signed-off-by: ZheNing Hu <adlternative@gmail.com>
> > ---
> >     git-difftool-helper.sh: learn a new way skip to save point
> >
> >     git user may should travel the diff list to choice file diff to view, if
> >     they exit in midway,they must travel it again. By saving current
> >     coordinates in GIT_DIR/difftool-last-position method, provides a
> >     possibility for this user-friendly solution.
> >
> >     this patch's origin discuss is here:
> >     https://lore.kernel.org/git/gOXOaoqn-E9A2ob7ykWEcDc7ZxmSwAjcP5CCFKfr5ejCOWZQ1lfAUZcbgYT9AyQCcDgJvCrnrtziXiels-Hxol3xlkGTVHk24SvAdaSUtKQ=@rtzoeller.com/
> >
> >     Thanks!
> >
> > Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-870%2Fadlternative%2Fdifftool_save_point-v2
> > Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-870/adlternative/difftool_save_point-v2
> > Pull-Request: https://github.com/gitgitgadget/git/pull/870
> >
> > Range-diff vs v1:
> >
> >  1:  e77c3e33ba85 ! 1:  2468eaff322b git-difftool-helper.sh: learn a new way skip to save point
> >      @@ Metadata
> >       Author: ZheNing Hu <adlternative@gmail.com>
> >
> >        ## Commit message ##
> >      -    git-difftool-helper.sh: learn a new way skip to save point
> >      +    git-difftool-helper.sh: learn a new way go back to last save point
> >
> >      -    `git difftool` only allow us to select file to view In turn.
> >      -    If there is a commit with many files and we exit in search,
> >      +    `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:every time before
> >      -    we view the file diff,the current coordinates will be stored in
> >      -    `GIT_DIR/difftool_skip_to`,this file will be deleted after
> >      -    successful traversing.But if an unexpected exit occurred midway,
> >      -    git will view the coordinates in the save point,ask user if they
> >      -    want continue from the last saved point.This will improve the
> >      -    user experience.
> >      +    we want to see. Therefore, here is a new method: every time before
> >      +    we view the file diff, the current coordinates will be stored in
> >      +    `GIT_DIR/difftool-last-position`, this file will be deleted after
> >      +    successful traversing. But if an unexpected exit occurred midway or
> >      +    users similar to using "ctrl+c" kill the process,and the user wants
> >      +    to redo the same `git difftoool`, git will view the coordinates in
> >      +    the save point, ask user if they want continue from the last position.
> >      +    This will improve the user experience.
> >
> >           Signed-off-by: ZheNing Hu <adlternative@gmail.com>
> >
> >      @@ git-difftool--helper.sh
> >        # Copyright (c) 2009, 2010 David Aguilar
> >
> >        TOOL_MODE=diff
> >      -+GIT_DIFFTOOL_SKIP_TO_FILE="$GIT_DIR/difftool-skip-to"
> >      ++GIT_DIFFTOOL_LAST_POSITION="$GIT_DIR/difftool-last-position"
> >      ++DIFFTOOL_FIRST_NUM="1"
> >        . git-mergetool--lib
> >
> >        # difftool.prompt controls the default prompt/no-prompt behavior
> >      @@ git-difftool--helper.sh: launch_merge_tool () {
> >         # the user with the real $MERGED name before launching $merge_tool.
> >         if should_prompt
> >         then
> >      -+         if test -f "$GIT_DIFFTOOL_SKIP_TO_FILE"
> >      ++         if test -f "$GIT_DIFFTOOL_LAST_POSITION"
> >       +         then
> >      -+                 SAVE_POINT_NUM=$(cat "$GIT_DIFFTOOL_SKIP_TO_FILE")
> >      -+                 if test $SAVE_POINT_NUM -le $GIT_DIFF_PATH_TOTAL &&
> >      -+                         test $SAVE_POINT_NUM -gt $GIT_DIFF_PATH_COUNTER
> >      ++                 if SAVE_POINT_NUM=$(cat 2>/dev/null "$GIT_DIFFTOOL_LAST_POSITION") &&
> >      ++                         test "$SAVE_POINT_NUM" -le "$GIT_DIFF_PATH_TOTAL" &&
> >      ++                                 test "$SAVE_POINT_NUM" -gt "$GIT_DIFF_PATH_COUNTER"
> >       +                 then
> >      -+                         # choice skip or not skip when check first file.
> >      -+                         if test $GIT_DIFF_PATH_COUNTER -eq "1"
> >      ++                         if test "$GIT_DIFF_PATH_COUNTER" -eq "$DIFFTOOL_FIRST_NUM"
> >       +                         then
> >      -+                                 printf "do you want to skip to last time difftool save point($SAVE_POINT_NUM) [Y/n]?"
> >      ++                                 printf "Do you want to start from the possible last file you were viewing? [Y/n]?"
> >       +                                 read skip_ans || return
> >       +                                 if test "$skip_ans" = y
> >       +                                 then
> >      @@ git-difftool--helper.sh: launch_merge_tool () {
> >       +                         fi
> >       +                 fi
> >       +         fi
>
>
> Similar to Junio's question about, "where does this possible come
> from?", I wasn't able to make out the behavior in the following
> situation.
>
> What about when the user switches branches or specifies a pathspec on
> the command-line or some other avenue that ends up with the number of
> files to diff being very different than the last difftool invocation?
>
> Will difftool, for example, skip over a smaller set of files on
> invocation 2 if invocation 1 involved many files and we exited out
> with a counter number that is very high?
>

> I don't want this to seem like I'm trying to be dismissive of this
> feature which does seem like a useful thing in general, so I'll try to
> come up with an alternative interface that is slightly more general
> but a admittedly a little bit more cumbersome because it's not as
> automatic.
>
> What if instead of global state, maybe the user could specify a path
> that difftool could skip forward to?   For example, we could teach
> difftool to resume by telling it where we last left off:
>
>    git difftool --resume-from=foo/bar099.txt
>
> Then we don't need the global counter state file?
>

>
> Finally, I'm going to plug what I believe to be the right tool for the
> job here.  Have you tried git cola?[1]  Difftool is tightly
> integrated, and the UI is such that you can trivially choose any of
> the modified/staged files and difftool them by using the Ctrl-d
> hotkey.
>
> https://github.com/git-cola/git-cola/
>
> Cola is purpose-built for driving difftool, and for interactive
> staging, so not mentioning it in the context of wanting a better UI
> for difftool would be a disservice to difftool users.