plypatch 0.4.1

Ply: Git-based Patch Management

Description

ply is a utility to manage a series of patches against an upstream project. These patches are stored as files in a separate git repositiory so that they can themselves be versioned. These patches can then be applied to create a patched version of the code to be used for packaging and deployment.

Concepts

The upstream project resides in the upstream-repo (UR). Your local checkout of the upstream-repo is called the working-repo and is where you’ll do most of your work: you’ll make changes, commit them, and then run ply save to create a new set of patches, called a patch-series.

The patches are stored in the patch-repo (PR), a separate git repo that is linked to the working-repo using the ply.patchrepo git config.

Usage

• Initialize a new patch-repo which initializes the new git repo and commits an empty series file:

  ply init .

• Link working-repo to a patch-repo:

  ply link ../my-patch-repo  # from within the working-repo

• Unlink working-repo from current patch-repo:

  ply unlink

• Check that status of a working-repo:

  ply status
  All patches applied

• Save set of commits to the patch-repo:

  # Without --since, any 'new' patches (patches that follow applied patches)
  # will be saved
  ply save
  
  # Save only the last commit into the 'foo' subdirectory
  ply save --since=HEAD^ --prefix=foo HEAD^

• Rollback working-repo to match upstream:

  ply rollback

• Restore patch-series:

  ply restore

• Resolve a failed merge and continue applying patch-series:

  ply resolve

• Skip a patch that has already merged upstream. In addition to performing a git am --skip, this will also remove the relevant patch from the patch-repo:

  ply skip

  Note: If the upstream patch is an exact match of the version in the patch-repo, ply will automatically remove the patch from the patch-repo.

• Perform a health-check on the patch-repo. This ensures that all of the patches in the patch-repo are accounted for in the patch-series:

  ply check
  OK

• Create a DOT graph representation of patch dependencies:

  ply graph

  The output of this can be piped into dot to generate a PNG file:

  ply graph | dot -Tpng > dependencies.png

ply vs X?

Tools for managing patches have existed for a while, so why create another?

The short answer is:

quilt deals in patch-files which can be versioned but doesn’t understand version-control. This orthogonality, in some respect, is elegant, but is a hassle in day-to-day use. Why checkpoint files in quilt when your version control system already does that for you?

stgit (stacked-git) understands version control but stores patches as commit objects, not as patch files. This means you can’t version your patches, making it impossible to rollback when things go awry.

ply blends these two tools together to create a tool that understands version-control but at the same time stores patches as files which can themselves be versioned.