Re: Summer of Code project ideas due this Friday

Jonathan Nieder wrote:

Some stuff off the top of my head, please apply a similar filter:

* Word-based merge helper

  The existing merge algorithms are all tailored to line-based formats
  such as code.  Writing, e.g., LaTeX or even asciidoc requires
  sticking to a strict word-wrapped format.  Worse even, re-wrapping
  leads to headaches if people work on the same areas a lot, much like
  the effects of code reindents.

  Something similar was already proposed in 2010, IIRC by Dscho:

    https://git.wiki.kernel.org/index.php/SoC2010Ideas#Merge_helper_for_LaTeX_files

  One possible angle of attack given --word-diff=porcelain would be:

  1. Fix --word-diff to properly represent both sides of the diff at
     least optionally.  (It was observed in a list post some months
     ago that it doesn't even represent *one* side faithfully.)

  2. Use --word-diff=porcelain as input to some to-be-written merge
     algorithm.

* Clean up add -p

  git-add--interactive.perl became a bit of a mess.  Partly due to my
  own efforts with {checkout,stash,...} it has bolted-on interfaces to
  other commands.  There are some UI issues that simply fall out of
  its design, e.g., you cannot go back from one file to another,
  Ctrl-C stops applying to the current file but does not discard
  earlier files, etc.  And that's not saying anything about 'add -i'
  which I don't really know.

  This would probably not be a very fun project, but it could add a
  little edge of usability to the tool and it's probably one of the
  few pure-Perl ideas we can offer.

I would phrase this as follows:

* fast-import-filter

  Implement a utility that can execute certain transformations to
  fast-import streams, such as:

  - delete or rename entire files/directories
  - split out subtrees
  - ...

  Ideally, this should be a thin command line interface around a set
  of primitives (such as a Perl package) that allow a competent
  scripter to go beyond the CLI.  (There have been threads on this.)

  Later on, make an interface that automatically does

    git fast-export | fast-import-filter | git fast-import

  with suitable options.  Nice because it should be largely orthogonal
  to everything except the fast-import stream format.

In addition, Jeff wrote:

I'd be interested to hear how that goes, because I think the tools are fundamentally different. The rebase and thus sequencer family is delta-based, and the fast-import and filter-branch families are tree-based. Feel free to prove me wrong of course.