wiki:GitRepoReorganization

Git Repository Reorganization (#8545)

The content on this page is still work in progress

Current state

As of db19c665ec5055c2193b2174519866045aeff09a all repos except for ghc-tarballs have been turned into proper submodules in in the master branch. GHC 7.10 will be the first release having proper submodules in place.

The following repositories are currently submodules: binary.git bytestring.git Cabal.git containers.git haskeline.git pretty.git primitive.git random.git terminfo.git time.git transformers.git vector.git Win32.git xhtml.git

As a crude statistics, the number of git push operations performed to the master branches of non-git-submodules between 2013-08-10 and 2013-11-23:

      2 packages/haskell2010
      2 packages/old-locale
      3 hsc2hs
      3 packages/haskell98
      3 packages/hoopl
      3 packages/hpc
      4 packages/old-time
      5 packages/deepseq
      5 packages/dph
      5 packages/integer-simple
      6 packages/parallel
      6 packages/stm
      7 nofib
      7 packages/filepath
      8 packages/array
      9 haddock
      9 packages/directory
     11 packages/ghc-prim
     11 packages/integer-gmp
     13 packages/template-haskell
     14 packages/process
     21 packages/unix
     59 packages/base
    176 testsuite
    347 ghc

Moreover, the following packages are tightly coupled to specific GHC versions (and are not supposed be cabal installable)

  • base
  • ghc-prim
  • integer-gmp/integer-simple
  • template-haskell

Some misc. notes about submodules

See also some older notes: DarcsConversion#Theperspectiveonsubmodules

  • based on the current access patterns, a few repositories are modified often (specifically, ghc.git and testsuite.git are often updated in a inter-dependent way); most repositories aren't updated for several weeks; therefore some of the issues outlined with the usability of submodules might have less weight here.

Simple migration plan

The plan

Fold some high-frequency repositories directly into ghc.git:

  • testsuite.git (commits to testsuite.git are tightly coupled to associated commits to ghc.git most of the time, and occur often)
  • base.git (tightly coupled to GHC internals, 3rd most often updated repo, often coupled with testsuite.git tweaks)
  • not so clear but potential candidates: ghc-prim.git, integer-gmp.git, integer-simple.git, template-haskell.git

Reasons for folding some repos into ghc.git:

  • Avoid overhead/noise of frequent git-submodule ref update commits to ghc.git
  • Simplify history (i.e. interlocked changes to ghc.git & testsuite.git are one single atomic commit/patch)

Reasons against folding all repos into ghc.git:

  • ghc.git repo (history) size
  • sparse/partial checkouts (e.g. via cabal get -s) require to fetch all of ghc.git's history

The remaining add-on repositories shall be converted into Git submodules.

The consequences

  • ghc.git's commit id by itself effectively provides a sufficient source-tree fingerprint; therefore, this renders the fingerprint.py superfluous
  • git bisect works (almost) out of the box now
  • buildbots don't need to fetch all repos every time to check for new commits; it's enough to check ghc.git, and only if a new commit in ghc.git exists, run git submodule update
Last modified 2 weeks ago Last modified on Jun 25, 2014 11:09:27 AM