view tests/test-share-safe.t @ 46149:294d5aca4ff5

copies: iterate over children directly (instead of parents) Before this change we would gather all parent → child edges and iterate on all parent, gathering copy information for children and aggregating them from there. They are not strict requirement for edges to be processed in that specific order. We could also simply iterate over all "children" revision and aggregate data from both parents at the same time. This patch does that. It make various things simpler: * since both parents are processed at the same time, we no longer need to cache data for merge (see next changeset for details), * we no longer need nested loop to process data, * we no longer need to store partial merge data for a rev from distinct loop interaction to another when processing merges, * we no longer need to build a full parent -> children mapping (we only rely on a simpler "parent -> number of children" map (for memory efficiency), * the data access pattern is now simpler (from lower revisions to higher revisions) and entirely predicable. That predictability open the way to prefetching and parallel processing. So that new iterations order requires simpler code and open the way to interesting optimisation. The effect on performance is quite good. In the worse case, we don't see any significant negative impact. And in the best case, the reduction of roundtrip to Python provide us with a significant speed. Some example below: Repo Case Source-Rev Dest-Rev # of revisions old time new time Difference Factor time per rev --------------------------------------------------------------------------------------------------------------------------------------------------------------- mozilla-try x00000_revs_x00000_added_0_copies dc8a3ca7010e d16fde900c9c : 34414 revs, 0.962867 s, 0.502584 s, -0.460283 s, × 0.5220, 14 µs/rev mozilla-try x0000_revs_xx000_added_x_copies 156f6e2674f2 4d0f2c178e66 : 8598 revs, 0.110717 s, 0.076323 s, -0.034394 s, × 0.6894, 8 µs/rev # full comparison between the previous changeset and this one Repo Case Source-Rev Dest-Rev # of revisions old time new time Difference Factor time per rev --------------------------------------------------------------------------------------------------------------------------------------------------------------- mercurial x_revs_x_added_0_copies ad6b123de1c7 39cfcef4f463 : 1 revs, 0.000048 s, 0.000041 s, -0.000007 s, × 0.8542, 41 µs/rev mercurial x_revs_x_added_x_copies 2b1c78674230 0c1d10351869 : 6 revs, 0.000153 s, 0.000102 s, -0.000051 s, × 0.6667, 17 µs/rev mercurial x000_revs_x000_added_x_copies 81f8ff2a9bf2 dd3267698d84 : 1032 revs, 0.004209 s, 0.004254 s, +0.000045 s, × 1.0107, 4 µs/rev pypy x_revs_x_added_0_copies aed021ee8ae8 099ed31b181b : 9 revs, 0.000203 s, 0.000282 s, +0.000079 s, × 1.3892, 31 µs/rev pypy x_revs_x000_added_0_copies 4aa4e1f8e19a 359343b9ac0e : 1 revs, 0.000059 s, 0.000048 s, -0.000011 s, × 0.8136, 48 µs/rev pypy x_revs_x_added_x_copies ac52eb7bbbb0 72e022663155 : 7 revs, 0.000194 s, 0.000211 s, +0.000017 s, × 1.0876, 30 µs/rev pypy x_revs_x00_added_x_copies c3b14617fbd7 ace7255d9a26 : 1 revs, 0.000380 s, 0.000375 s, -0.000005 s, × 0.9868, 375 µs/rev pypy x_revs_x000_added_x000_copies df6f7a526b60 a83dc6a2d56f : 6 revs, 0.010588 s, 0.010574 s, -0.000014 s, × 0.9987, 1762 µs/rev pypy x000_revs_xx00_added_0_copies 89a76aede314 2f22446ff07e : 4785 revs, 0.048961 s, 0.049974 s, +0.001013 s, × 1.0207, 10 µs/rev pypy x000_revs_x000_added_x_copies 8a3b5bfd266e 2c68e87c3efe : 6780 revs, 0.083612 s, 0.084300 s, +0.000688 s, × 1.0082, 12 µs/rev pypy x000_revs_x000_added_x000_copies 89a76aede314 7b3dda341c84 : 5441 revs, 0.058579 s, 0.060128 s, +0.001549 s, × 1.0264, 11 µs/rev pypy x0000_revs_x_added_0_copies d1defd0dc478 c9cb1334cc78 : 43645 revs, 0.736783 s, 0.686542 s, -0.050241 s, × 0.9318, 15 µs/rev pypy x0000_revs_xx000_added_0_copies bf2c629d0071 4ffed77c095c : 2 revs, 0.022050 s, 0.009277 s, -0.012773 s, × 0.4207, 4638 µs/rev pypy x0000_revs_xx000_added_x000_copies 08ea3258278e d9fa043f30c0 : 11316 revs, 0.120800 s, 0.114733 s, -0.006067 s, × 0.9498, 10 µs/rev netbeans x_revs_x_added_0_copies fb0955ffcbcd a01e9239f9e7 : 2 revs, 0.000140 s, 0.000081 s, -0.000059 s, × 0.5786, 40 µs/rev netbeans x_revs_x000_added_0_copies 6f360122949f 20eb231cc7d0 : 2 revs, 0.000114 s, 0.000107 s, -0.000007 s, × 0.9386, 53 µs/rev netbeans x_revs_x_added_x_copies 1ada3faf6fb6 5a39d12eecf4 : 3 revs, 0.000224 s, 0.000173 s, -0.000051 s, × 0.7723, 57 µs/rev netbeans x_revs_x00_added_x_copies 35be93ba1e2c 9eec5e90c05f : 9 revs, 0.000723 s, 0.000698 s, -0.000025 s, × 0.9654, 77 µs/rev netbeans x000_revs_xx00_added_0_copies eac3045b4fdd 51d4ae7f1290 : 1421 revs, 0.009665 s, 0.009248 s, -0.000417 s, × 0.9569, 6 µs/rev netbeans x000_revs_x000_added_x_copies e2063d266acd 6081d72689dc : 1533 revs, 0.014820 s, 0.015446 s, +0.000626 s, × 1.0422, 10 µs/rev netbeans x000_revs_x000_added_x000_copies ff453e9fee32 411350406ec2 : 5750 revs, 0.076049 s, 0.074373 s, -0.001676 s, × 0.9780, 12 µs/rev netbeans x0000_revs_xx000_added_x000_copies 588c2d1ced70 1aad62e59ddd : 66949 revs, 0.683603 s, 0.639870 s, -0.043733 s, × 0.9360, 9 µs/rev mozilla-central x_revs_x_added_0_copies 3697f962bb7b 7015fcdd43a2 : 2 revs, 0.000161 s, 0.000088 s, -0.000073 s, × 0.5466, 44 µs/rev mozilla-central x_revs_x000_added_0_copies dd390860c6c9 40d0c5bed75d : 8 revs, 0.000234 s, 0.000199 s, -0.000035 s, × 0.8504, 24 µs/rev mozilla-central x_revs_x_added_x_copies 8d198483ae3b 14207ffc2b2f : 9 revs, 0.000247 s, 0.000171 s, -0.000076 s, × 0.6923, 19 µs/rev mozilla-central x_revs_x00_added_x_copies 98cbc58cc6bc 446a150332c3 : 7 revs, 0.000630 s, 0.000592 s, -0.000038 s, × 0.9397, 84 µs/rev mozilla-central x_revs_x000_added_x000_copies 3c684b4b8f68 0a5e72d1b479 : 3 revs, 0.003286 s, 0.003151 s, -0.000135 s, × 0.9589, 1050 µs/rev mozilla-central x_revs_x0000_added_x0000_copies effb563bb7e5 c07a39dc4e80 : 6 revs, 0.062441 s, 0.061612 s, -0.000829 s, × 0.9867, 10268 µs/rev mozilla-central x000_revs_xx00_added_0_copies 6100d773079a 04a55431795e : 1593 revs, 0.005423 s, 0.005381 s, -0.000042 s, × 0.9923, 3 µs/rev mozilla-central x000_revs_x000_added_x_copies 9f17a6fc04f9 2d37b966abed : 41 revs, 0.005919 s, 0.003742 s, -0.002177 s, × 0.6322, 91 µs/rev mozilla-central x000_revs_x000_added_x000_copies 7c97034feb78 4407bd0c6330 : 7839 revs, 0.062597 s, 0.061983 s, -0.000614 s, × 0.9902, 7 µs/rev mozilla-central x0000_revs_xx000_added_0_copies 9eec5917337d 67118cc6dcad : 615 revs, 0.043551 s, 0.019861 s, -0.023690 s, × 0.4560, 32 µs/rev mozilla-central x0000_revs_xx000_added_x000_copies f78c615a656c 96a38b690156 : 30263 revs, 0.192475 s, 0.188101 s, -0.004374 s, × 0.9773, 6 µs/rev mozilla-central x00000_revs_x0000_added_x0000_copies 6832ae71433c 4c222a1d9a00 : 153721 revs, 1.955575 s, 1.806696 s, -0.148879 s, × 0.9239, 11 µs/rev mozilla-central x00000_revs_x00000_added_x000_copies 76caed42cf7c 1daa622bbe42 : 204976 revs, 2.886501 s, 2.682987 s, -0.203514 s, × 0.9295, 13 µs/rev mozilla-try x_revs_x_added_0_copies aaf6dde0deb8 9790f499805a : 2 revs, 0.001181 s, 0.000852 s, -0.000329 s, × 0.7214, 426 µs/rev mozilla-try x_revs_x000_added_0_copies d8d0222927b4 5bb8ce8c7450 : 2 revs, 0.001189 s, 0.000859 s, -0.000330 s, × 0.7225, 429 µs/rev mozilla-try x_revs_x_added_x_copies 092fcca11bdb 936255a0384a : 4 revs, 0.000563 s, 0.000150 s, -0.000413 s, × 0.2664, 37 µs/rev mozilla-try x_revs_x00_added_x_copies b53d2fadbdb5 017afae788ec : 2 revs, 0.001548 s, 0.001158 s, -0.000390 s, × 0.7481, 579 µs/rev mozilla-try x_revs_x000_added_x000_copies 20408ad61ce5 6f0ee96e21ad : 1 revs, 0.027782 s, 0.027240 s, -0.000542 s, × 0.9805, 27240 µs/rev mozilla-try x_revs_x0000_added_x0000_copies effb563bb7e5 c07a39dc4e80 : 6 revs, 0.062781 s, 0.062824 s, +0.000043 s, × 1.0007, 10470 µs/rev mozilla-try x000_revs_xx00_added_0_copies 6100d773079a 04a55431795e : 1593 revs, 0.005778 s, 0.005463 s, -0.000315 s, × 0.9455, 3 µs/rev mozilla-try x000_revs_x000_added_x_copies 9f17a6fc04f9 2d37b966abed : 41 revs, 0.006192 s, 0.004238 s, -0.001954 s, × 0.6844, 103 µs/rev mozilla-try x000_revs_x000_added_x000_copies 1346fd0130e4 4c65cbdabc1f : 6657 revs, 0.065391 s, 0.064113 s, -0.001278 s, × 0.9805, 9 µs/rev mozilla-try x0000_revs_x_added_0_copies 63519bfd42ee a36a2a865d92 : 40314 revs, 0.317216 s, 0.294063 s, -0.023153 s, × 0.9270, 7 µs/rev mozilla-try x0000_revs_x_added_x_copies 9fe69ff0762d bcabf2a78927 : 38690 revs, 0.303119 s, 0.281493 s, -0.021626 s, × 0.9287, 7 µs/rev mozilla-try x0000_revs_xx000_added_x_copies 156f6e2674f2 4d0f2c178e66 : 8598 revs, 0.110717 s, 0.076323 s, -0.034394 s, × 0.6894, 8 µs/rev mozilla-try x0000_revs_xx000_added_0_copies 9eec5917337d 67118cc6dcad : 615 revs, 0.045739 s, 0.020390 s, -0.025349 s, × 0.4458, 33 µs/rev mozilla-try x0000_revs_xx000_added_x000_copies 89294cd501d9 7ccb2fc7ccb5 : 97052 revs, 3.098021 s, 3.023879 s, -0.074142 s, × 0.9761, 31 µs/rev mozilla-try x0000_revs_x0000_added_x0000_copies e928c65095ed e951f4ad123a : 52031 revs, 0.771480 s, 0.735549 s, -0.035931 s, × 0.9534, 14 µs/rev mozilla-try x00000_revs_x_added_0_copies 6a320851d377 1ebb79acd503 : 363753 revs, 18.813422 s, 18.568900 s, -0.244522 s, × 0.9870, 51 µs/rev mozilla-try x00000_revs_x00000_added_0_copies dc8a3ca7010e d16fde900c9c : 34414 revs, 0.962867 s, 0.502584 s, -0.460283 s, × 0.5220, 14 µs/rev mozilla-try x00000_revs_x_added_x_copies 5173c4b6f97c 95d83ee7242d : 362229 revs, 18.684923 s, 18.356645 s, -0.328278 s, × 0.9824, 50 µs/rev mozilla-try x00000_revs_x000_added_x_copies 9126823d0e9c ca82787bb23c : 359344 revs, 18.296305 s, 18.250393 s, -0.045912 s, × 0.9975, 50 µs/rev mozilla-try x00000_revs_x0000_added_x0000_copies 8d3fafa80d4b eb884023b810 : 192665 revs, 3.061887 s, 2.792459 s, -0.269428 s, × 0.9120, 14 µs/rev mozilla-try x00000_revs_x00000_added_x0000_copies 1b661134e2ca 1ae03d022d6d : 228985 revs, 103.869641 s, 107.697264 s, +3.827623 s, × 1.0369, 470 µs/rev mozilla-try x00000_revs_x00000_added_x000_copies 9b2a99adc05e 8e29777b48e6 : 382065 revs, 64.262957 s, 63.961040 s, -0.301917 s, × 0.9953, 167 µs/rev Differential Revision: https://phab.mercurial-scm.org/D9422
author Pierre-Yves David <pierre-yves.david@octobus.net>
date Mon, 14 Dec 2020 11:32:24 +0100
parents 6c960b708ac4
children 0babe12ef35d
line wrap: on
line source

setup

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > share =
  > [format]
  > exp-share-safe = True
  > EOF

prepare source repo

  $ hg init source
  $ cd source
  $ cat .hg/requires
  exp-sharesafe
  $ cat .hg/store/requires
  dotencode
  fncache
  generaldelta
  revlogv1
  sparserevlog
  store
  $ hg debugrequirements
  dotencode
  exp-sharesafe
  fncache
  generaldelta
  revlogv1
  sparserevlog
  store

  $ echo a > a
  $ hg ci -Aqm "added a"
  $ echo b > b
  $ hg ci -Aqm "added b"

  $ HGEDITOR=cat hg config --shared
  abort: repository is not shared; can't use --shared
  [10]
  $ cd ..

Create a shared repo and check the requirements are shared and read correctly
  $ hg share source shared1
  updating working directory
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd shared1
  $ cat .hg/requires
  exp-sharesafe
  shared

  $ hg debugrequirements -R ../source
  dotencode
  exp-sharesafe
  fncache
  generaldelta
  revlogv1
  sparserevlog
  store

  $ hg debugrequirements
  dotencode
  exp-sharesafe
  fncache
  generaldelta
  revlogv1
  shared
  sparserevlog
  store

  $ echo c > c
  $ hg ci -Aqm "added c"

Check that config of the source repository is also loaded

  $ hg showconfig ui.curses
  [1]

  $ echo "[ui]" >> ../source/.hg/hgrc
  $ echo "curses=true" >> ../source/.hg/hgrc

  $ hg showconfig ui.curses
  true

Test that extensions of source repository are also loaded

  $ hg debugextensions
  share
  $ hg extdiff -p echo
  hg: unknown command 'extdiff'
  'extdiff' is provided by the following extension:
  
      extdiff       command to allow external programs to compare revisions
  
  (use 'hg help extensions' for information on enabling extensions)
  [255]

  $ echo "[extensions]" >> ../source/.hg/hgrc
  $ echo "extdiff=" >> ../source/.hg/hgrc

  $ hg debugextensions -R ../source
  extdiff
  share
  $ hg extdiff -R ../source -p echo

BROKEN: the command below will not work if config of shared source is not loaded
on dispatch but debugextensions says that extension
is loaded
  $ hg debugextensions
  extdiff
  share

  $ hg extdiff -p echo

However, local .hg/hgrc should override the config set by share source

  $ echo "[ui]" >> .hg/hgrc
  $ echo "curses=false" >> .hg/hgrc

  $ hg showconfig ui.curses
  false

  $ HGEDITOR=cat hg config --shared
  [ui]
  curses=true
  [extensions]
  extdiff=

  $ HGEDITOR=cat hg config --local
  [ui]
  curses=false

Testing that hooks set in source repository also runs in shared repo

  $ cd ../source
  $ cat <<EOF >> .hg/hgrc
  > [extensions]
  > hooklib=
  > [hooks]
  > pretxnchangegroup.reject_merge_commits = \
  >   python:hgext.hooklib.reject_merge_commits.hook
  > EOF

  $ cd ..
  $ hg clone source cloned
  updating to branch default
  3 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd cloned
  $ hg up 0
  0 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ echo bar > bar
  $ hg ci -Aqm "added bar"
  $ hg merge
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg ci -m "merge commit"

  $ hg push ../source
  pushing to ../source
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  error: pretxnchangegroup.reject_merge_commits hook failed: bcde3522682d rejected as merge on the same branch. Please consider rebase.
  transaction abort!
  rollback completed
  abort: bcde3522682d rejected as merge on the same branch. Please consider rebase.
  [255]

  $ hg push ../shared1
  pushing to ../shared1
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  error: pretxnchangegroup.reject_merge_commits hook failed: bcde3522682d rejected as merge on the same branch. Please consider rebase.
  transaction abort!
  rollback completed
  abort: bcde3522682d rejected as merge on the same branch. Please consider rebase.
  [255]

Test that if share source config is untrusted, we dont read it

  $ cd ../shared1

  $ cat << EOF > $TESTTMP/untrusted.py
  > from mercurial import scmutil, util
  > def uisetup(ui):
  >     class untrustedui(ui.__class__):
  >         def _trusted(self, fp, f):
  >             if util.normpath(fp.name).endswith(b'source/.hg/hgrc'):
  >                 return False
  >             return super(untrustedui, self)._trusted(fp, f)
  >     ui.__class__ = untrustedui
  > EOF

  $ hg showconfig hooks
  hooks.pretxnchangegroup.reject_merge_commits=python:hgext.hooklib.reject_merge_commits.hook

  $ hg showconfig hooks --config extensions.untrusted=$TESTTMP/untrusted.py
  [1]

Update the source repository format and check that shared repo works

  $ cd ../source

Disable zstd related tests because its not present on pure version
#if zstd
  $ echo "[format]" >> .hg/hgrc
  $ echo "revlog-compression=zstd" >> .hg/hgrc

  $ hg debugupgraderepo --run -q
  upgrade will perform the following actions:
  
  requirements
     preserved: dotencode, exp-sharesafe, fncache, generaldelta, revlogv1, sparserevlog, store
     added: revlog-compression-zstd
  
  processed revlogs:
    - all-filelogs
    - changelog
    - manifest
  
  $ hg log -r .
  changeset:   1:5f6d8a4bf34a
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     added b
  
#endif
  $ echo "[format]" >> .hg/hgrc
  $ echo "use-persistent-nodemap=True" >> .hg/hgrc

  $ hg debugupgraderepo --run -q -R ../shared1
  abort: cannot upgrade repository; unsupported source requirement: shared
  [255]

  $ hg debugupgraderepo --run -q
  upgrade will perform the following actions:
  
  requirements
     preserved: dotencode, exp-sharesafe, fncache, generaldelta, revlogv1, sparserevlog, store (no-zstd !)
     preserved: dotencode, exp-sharesafe, fncache, generaldelta, revlog-compression-zstd, revlogv1, sparserevlog, store (zstd !)
     added: persistent-nodemap
  
  processed revlogs:
    - all-filelogs
    - changelog
    - manifest
  
  $ hg log -r .
  changeset:   1:5f6d8a4bf34a
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     added b
  

Shared one should work
  $ cd ../shared1
  $ hg log -r .
  changeset:   2:155349b645be
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     added c
  

Testing that nonsharedrc is loaded for source and not shared

  $ cd ../source
  $ touch .hg/hgrc-not-shared
  $ echo "[ui]" >> .hg/hgrc-not-shared
  $ echo "traceback=true" >> .hg/hgrc-not-shared

  $ hg showconfig ui.traceback
  true

  $ HGEDITOR=cat hg config --non-shared
  [ui]
  traceback=true

  $ cd ../shared1
  $ hg showconfig ui.traceback
  [1]

Unsharing works

  $ hg unshare

Test that source config is added to the shared one after unshare, and the config
of current repo is still respected over the config which came from source config
  $ cd ../cloned
  $ hg push ../shared1
  pushing to ../shared1
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  error: pretxnchangegroup.reject_merge_commits hook failed: bcde3522682d rejected as merge on the same branch. Please consider rebase.
  transaction abort!
  rollback completed
  abort: bcde3522682d rejected as merge on the same branch. Please consider rebase.
  [255]
  $ hg showconfig ui.curses -R ../shared1
  false

  $ cd ../

Test that upgrading using debugupgraderepo works
=================================================

  $ hg init non-share-safe --config format.exp-share-safe=false
  $ cd non-share-safe
  $ hg debugrequirements
  dotencode
  fncache
  generaldelta
  revlogv1
  sparserevlog
  store
  $ echo foo > foo
  $ hg ci -Aqm 'added foo'
  $ echo bar > bar
  $ hg ci -Aqm 'added bar'

Create a share before upgrading

  $ cd ..
  $ hg share non-share-safe nss-share
  updating working directory
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg debugrequirements -R nss-share
  dotencode
  fncache
  generaldelta
  revlogv1
  shared
  sparserevlog
  store
  $ cd non-share-safe

Upgrade

  $ hg debugupgraderepo -q
  requirements
     preserved: dotencode, fncache, generaldelta, revlogv1, sparserevlog, store
     added: exp-sharesafe
  
  processed revlogs:
    - all-filelogs
    - changelog
    - manifest
  
  $ hg debugupgraderepo --run -q
  upgrade will perform the following actions:
  
  requirements
     preserved: dotencode, fncache, generaldelta, revlogv1, sparserevlog, store
     added: exp-sharesafe
  
  processed revlogs:
    - all-filelogs
    - changelog
    - manifest
  
  repository upgraded to share safe mode, existing shares will still work in old non-safe mode. Re-share existing shares to use them in safe mode New shares will be created in safe mode.

  $ hg debugrequirements
  dotencode
  exp-sharesafe
  fncache
  generaldelta
  revlogv1
  sparserevlog
  store

  $ cat .hg/requires
  exp-sharesafe

  $ cat .hg/store/requires
  dotencode
  fncache
  generaldelta
  revlogv1
  sparserevlog
  store

  $ hg log -GT "{node}: {desc}\n"
  @  f63db81e6dde1d9c78814167f77fb1fb49283f4f: added bar
  |
  o  f3ba8b99bb6f897c87bbc1c07b75c6ddf43a4f77: added foo
  

Make sure existing shares still works

  $ hg log -GT "{node}: {desc}\n" -R ../nss-share
  warning: source repository supports share-safe functionality. Reshare to upgrade.
  @  f63db81e6dde1d9c78814167f77fb1fb49283f4f: added bar
  |
  o  f3ba8b99bb6f897c87bbc1c07b75c6ddf43a4f77: added foo
  


Create a safe share from upgrade one

  $ cd ..
  $ hg share non-share-safe ss-share
  updating working directory
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd ss-share
  $ hg log -GT "{node}: {desc}\n"
  @  f63db81e6dde1d9c78814167f77fb1fb49283f4f: added bar
  |
  o  f3ba8b99bb6f897c87bbc1c07b75c6ddf43a4f77: added foo
  
  $ cd ../non-share-safe

Test that downgrading works too

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > share =
  > [format]
  > exp-share-safe = False
  > EOF

  $ hg debugupgraderepo -q
  requirements
     preserved: dotencode, fncache, generaldelta, revlogv1, sparserevlog, store
     removed: exp-sharesafe
  
  processed revlogs:
    - all-filelogs
    - changelog
    - manifest
  
  $ hg debugupgraderepo -q --run
  upgrade will perform the following actions:
  
  requirements
     preserved: dotencode, fncache, generaldelta, revlogv1, sparserevlog, store
     removed: exp-sharesafe
  
  processed revlogs:
    - all-filelogs
    - changelog
    - manifest
  
  repository downgraded to not use share safe mode, existing shares will not work and needs to be reshared.

  $ hg debugrequirements
  dotencode
  fncache
  generaldelta
  revlogv1
  sparserevlog
  store

  $ cat .hg/requires
  dotencode
  fncache
  generaldelta
  revlogv1
  sparserevlog
  store

  $ test -f .hg/store/requires
  [1]

  $ hg log -GT "{node}: {desc}\n"
  @  f63db81e6dde1d9c78814167f77fb1fb49283f4f: added bar
  |
  o  f3ba8b99bb6f897c87bbc1c07b75c6ddf43a4f77: added foo
  

Make sure existing shares still works

  $ hg log -GT "{node}: {desc}\n" -R ../nss-share
  @  f63db81e6dde1d9c78814167f77fb1fb49283f4f: added bar
  |
  o  f3ba8b99bb6f897c87bbc1c07b75c6ddf43a4f77: added foo
  
  $ hg unshare -R ../nss-share

  $ hg log -GT "{node}: {desc}\n" -R ../ss-share
  abort: share source does not support exp-sharesafe requirement
  [255]