Getting a consistent tree from the past

[Geoffrey Mainland]

I would like to get a consistent tree by date. Right now I'm using this trick:

git checkout `git rev-list -n 1 --before="2012-12-19 17:42:09" master`

But this seems to use the author date instead of the committer date. For example, in libraries/base:

[gmainlan at MSRC-1361848 base]$ git checkout `git rev-list -n 1 --before="2012-12-19 17:42:09" master`
HEAD is now at 1d97ad1... Use sharing in the Alternative instance of Maybe
[gmainlan at MSRC-1361848 base]$ git log | head                                    commit 1d97ad10283d23b6dfb698a38ae57c29accd6ada
Author: Bas van Dijk <v.dijk.bas at gmail.com>
Date:   Wed Dec 14 12:24:38 2011 +0100

    Use sharing in the Alternative instance of Maybe

commit f99cee0118c6bbcd0283ea795a3bb6ff6090b5b5
Author: Bas van Dijk <v.dijk.bas at gmail.com>
Date:   Sat Oct 29 03:33:08 2011 +0200

[gmainlan at MSRC-1361848 base]$

The committer date for this commit is 2012-01-14, well past "2012-12-19 17:42:09"!

In general, how is one supposed to get a consistent tree from the past? Git submodules solve this problem, and I know there was some debate about using them for the GHC repo. SCM is failing if one can't get a consistent C from the past!

As a side note, fingerprint.py seems to be doing something funny:

[gmainlan at MSRC-1361848 ghc-simd-test]$ ./utils/fingerprint/fingerprint.py create | head
.|ee2dad13f8a3cd484f25aa949895535d6eb0f15e
ghc-tarballs|01a8e25294fd5d501e0db115debafd4fd61970a0
libraries/Cabal|10098d3709e9febe14675f5eeaa6a4f4a42bd4c1
libraries/Win32|2b3c43c6fa3ffe85baa6413ce80fc6ce5cc17acf
libraries/array|fa295423e7404d3d1d3d82655b2b44d50f045a44
libraries/base|7ed7dd84f5e7664d127f329708a230fdabcc2cf8
libraries/binary|376797487651cf995bd52458ce1f7d7a283341b3
libraries/bytestring|7bdf7129d0f76812f4310735a0fe75dc6bbeee3b
libraries/containers|1ad907a244e163191cdc0679083c72d2309b1426
libraries/deepseq|835cad358b10fe5e6a4f2c38ce1286f5c6fd0d30
[gmainlan at MSRC-1361848 ghc-simd-test]$ git log | head
commit 51ccfa90a8d61a4728ca643c1809cb96cc600836
Merge: e83973b 44e1853
Author: Geoffrey Mainland <gmainlan at microsoft.com>
Date:   Tue Jan 17 08:03:50 2012 +0000

    Merge commit '44e18534a9d84572047af2' into simd

    Conflicts:
        compiler/prelude/TysPrim.lhs

[gmainlan at MSRC-1361848 ghc-simd-test]$

Should the fingerprint for "." be 51ccfa90a8d61a4728ca643c1809cb96cc600836!? ee2dad13f8a3cd484f25aa949895535d6eb0f15e is a commit back in late November...

Thanks,
Geoff
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