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Comment by antonkochubey | Hacker News Reader

Sorry for my ignorance, but what is the usefulness of undo persistence after a IDE restart? Don't you normally save your changes and finish a piece of work before exiting an DE?

Edit: some great examples in the replies here, thanks! Perhaps I should start using it in editors that support it, never gave it a thought before.

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The reason why this feature is particularly useful in vi-likes is because they are not IDEs. I hop in and out of vi all day long. Depending on the task I might create a new tab, run a command in vi, or exit vi to run it. Vi’s appeal is that it is “just” an editor and your terminal and workstation form your un-integrated development environment.

The whole point of undo is that you realize you made a mistake later. If you've done that after you've saved your changes and exited the program, you'd have no expectation of undo still working unless you've enabled this feature.

It doesn't matter whether or not you can think of a reason you would want to enable it, but it should be pretty trivial to do so. Once you've enabled it, it should work.

The article gave 2 examples.

I can give some as well. IDE crashes. Computer reboots at an undesired time. Even if my work is saved, I am not “finished”. I would like my undo history to extend before file / open time.

I often use it to edit system config files, often on embedded devices where I don't have my git credentials setup, or on servers. In these cases we're already not in an ideal world, I don't have good reliable version control or change management in place. In those less-than-ideal worlds, having proper undo history is nice.

    #!/bin/sh
    
    errecho() {
        >&2 printf '%s\n' "$@"
    }
    
    if [ "$#" != 1 ] || [ -z "$1" ]
    then
        errecho 'Requires a single filename as the argument'
        exit 1
    fi
    
    ORIGINAL=$1
    if [ "${ORIGINAL#./}" == "$ORIGINAL" ] && [ "${ORIGINAL#/}" == "$ORIGINAL" ]
    then
        ORIGINAL=./"$ORIGINAL"
    fi
    
    # because of course the output of dirname can't be blindly joined with slash and the basename
    DIRNAME=$(dirname -- "$ORIGINAL")
    if [ "$DIRNAME" = / ]
    then
        DIRNAME=
    fi
    
    FILENAME=$(basename -- "$ORIGINAL")
    # because of course extracting the filename's extension is not supported out of the box
    case "$FILENAME" in
        .*.* )
            EXTENSION=.${FILENAME#.*.}
            BASENAME=$(printf '%s' "$FILENAME" | cut -c-$((${#FILENAME} - ${#EXTENSION})) )
            ;;
        .* )
            EXTENSION=
            BASENAME=$FILENAME
            ;;
        *.[^.]* )
            BASENAME=${FILENAME%%.*}
            EXTENSION=${FILENAME#*.}
            ;;
        * )
            BASENAME=${FILENAME%%.*}
            EXTENSION=$(printf '%s' "$FILENAME" | cut -c$((${#BASENAME} + 1))- )
            ;;
    esac
    
    if [ "$FILENAME" != "$BASENAME$EXTENSION" ] || [ -z "$BASENAME" ]
    then
        errecho 'Failed to properly split the extension from the filename:' "$FILENAME"
        exit 1
    fi
    
    TIMESTAMP=$(date --utc --date=@"$(stat --format %Y "$ORIGINAL")" +'_%Y-%m-%d_%H%M%S')
    if [ -z "$TIMESTAMP" ]
    then
        errecho 'Failed to get the timestamp of the file:' "$ORIGINAL"
        exit 1
    fi
    
    NEW_FILENAME=$(printf '%s/%s_%s%s' "$DIRNAME" "$BASENAME" "$TIMESTAMP" "$EXTENSION")
    
    if [ "$NEW_FILENAME" = "$ORIGINAL" ]
    then
        errecho 'Somehow the name for the backup is the same as the original file'
        exit 1
    fi
    
    # this preserves the timestamps somewhat better
    if ! mv --no-clobber --no-copy -- "$ORIGINAL" "$NEW_FILENAME"
    then
        errecho 'Failed to backup the file: ' "$ORIGINAL" "$NEW_FILENAME"
        exit 1
    fi
    
    if ! cp -- "$NEW_FILENAME" "$ORIGINAL"
    then
        errecho 'Failed to backup the file: ' "$ORIGINAL" "$NEW_FILENAME"
        mv --no-clobber --no-copy -- "$NEW_FILENAME" "$ORIGINAL"
    fi

Actually, nevermind that bullshit, you know what? I think I'd prefer to have an editor with locally persisted edit history instead.

First, you need backups

Second (for servers), etckeeper

I mean I already responded to the comment

> In these cases we're already not in an ideal world, I don't have good reliable version control or change management in place.

Most of the stuff I work on is properly scripted idempotent deploys, with good backups and all that. Or it's a one-off demo, or a prototype. Not having full undo history is never going to actually kill a project, it's just going to make early stage projects and one-offs more inconvenient.

One silly example: sometimes I'll open up source or config file to make a quick, temporary change in order to test something. But then instead of ctrl+z backgrounding it, I'll accidentally quit vim. Then I start it back up to undo the change, and find that there's no undo history.

I didn't know about persistent undo until seeing this posted here on HN, but now I've enabled it! Of course, turns out it's an unreliable feature on nvim... maybe I'll consider switching back to the original (for that and other reasons).

Most apps don't have it, so you might not be used to it, but have you never wished that you could undo the changes you made after you restarted the program?

Moreover, the vim history tracking is amazingly advanced. It's almost like a mini version control system. I highly recommend getting to know it.

If your session / computer crashes, for one.

Another one:

`:earlier 1d`.

persistant undo is like a second brain to consolidate.

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