Add optional auto-update feature

[marlonrichert]

This needs to be smart enough that it does not try to update repos where the work tree is dirty or where you have unpushed commits.

Discussed in #97

^{Originally posted by xenoterracide August 4, 2021}
Does zsnap do any lazy evalution? such as I don't want to do any evaluation until conditions such as prompt available or command pattern matched for completion?

do you have any comparison times with other frameworks?

how does zsnap update plugins and itself? do I need to write a cron/timer?

[xenoterracide]

I still think that cron jobs should be enough, with sample files for system. I think I might go make a system bug asking for an implementation of crontab CLI or something; the dirty tree thing might still be a thing to enhance the update command.

[srobinson]

I still think that cron jobs should be enough, with sample files for system. I think I might go make a system bug asking for an implementation of crontab CLI or something; the dirty tree thing might still be a thing to enhance the update command.

git maintenance run will fetch hourly

[marlonrichert]

@srobinson But it doesn’t pull.

[hawktang]

need to add the function of self update

[marlonrichert]

@hawktang Please make a new issue for that.