sharesafe: introduce functionality to automatically upgrade shares

In past few months, we have developed a `share-safe` mode for sharing repository
in which share source requirements and config values are shared with the shares.

To get it rolling, an important task is to get these shares automatically
upgraded. We are focusing on an installation where shares are created by scripts
and test jobs. It will be difficult to manually upgrade these and we need some
functionality to do so automatically.

This patch introduces a config option to deal with it. If all of the following
conditions are met, we upgrade the share repository automatically:

* If the config option is enabled
* Share source repository is share-safe enabled
* Share is not share-safe enabled
* Any command is run in the share

Upgrading the share is pretty easy as it involves only editing the requirements
file.

Differential Revision: https://phab.mercurial-scm.org/D9679

mercurial/configitems.py

@@ -1074,6 +1074,11 b' coreconfigitem('
 )
 coreconfigitem(
     b'experimental',
+    b'sharesafe-auto-upgrade-shares',
+    default=False,
+)
+coreconfigitem(
+    b'experimental',
     b'single-head-per-branch',
     default=False,
 )

mercurial/localrepo.py

@@ -582,12 +582,23 b' def makelocalrepository(baseui, path, in'
     elif shared:
         sourcerequires = _readrequires(sharedvfs, False)
         if requirementsmod.SHARESAFE_REQUIREMENT in sourcerequires:
-            ui.warn(
-                _(
-                    b'warning: source repository supports share-safe functionality.'
-                    b' Reshare to upgrade.\n'
+            if ui.configbool(b'experimental', b'sharesafe-auto-upgrade-shares'):
+                # prevent cyclic import localrepo -> upgrade -> localrepo
+                from . import upgrade
+
+                upgrade.upgrade_share_to_safe(
+                    ui,
+                    hgvfs,
+                    storevfs,
+                    requirements,
                 )
-            )
+            else:
+                ui.warn(
+                    _(
+                        b'warning: source repository supports share-safe functionality.'
+                        b' Reshare to upgrade.\n'
+                    )
+                )
 
     # The .hg/hgrc file may load extensions or contain config options
     # that influence repository construction. Attempt to load it and

mercurial/upgrade.py

@@ -12,7 +12,10 b' from . import ('
     error,
     hg,
     localrepo,
+    lock as lockmod,
     pycompat,
+    requirements as requirementsmod,
+    scmutil,
 )
 
 from .upgrade_utils import (
@@ -20,6 +23,10 b' from .upgrade_utils import ('
     engine as upgrade_engine,
 )
 
+from .utils import (
+    stringutil,
+)
+
 allformatvariant = upgrade_actions.allformatvariant
 
 
@@ -232,3 +239,28 b' def upgraderepo('
                 )
 
             upgrade_op.print_post_op_messages()
+
+
+def upgrade_share_to_safe(ui, hgvfs, storevfs, current_requirements):
+    """Upgrades a share to use share-safe mechanism"""
+    wlock = None
+    try:
+        wlock = lockmod.trylock(ui, hgvfs, b'wlock', 0, 0)
+        store_requirements = localrepo._readrequires(storevfs, False)
+        # after upgrade, store requires will be shared, so lets find
+        # the requirements which are not present in store and
+        # write them to share's .hg/requires
+        diffrequires = current_requirements - store_requirements
+        # add share-safe requirement as it will mark the share as share-safe
+        diffrequires.add(requirementsmod.SHARESAFE_REQUIREMENT)
+        scmutil.writerequires(hgvfs, diffrequires)
+        current_requirements.add(requirementsmod.SHARESAFE_REQUIREMENT)
+        ui.warn(_(b'repository upgraded to use share-safe mode\n'))
+    except error.LockError as e:
+        ui.warn(
+            _(b'failed to upgrade share, got error: %s\n')
+            % stringutil.forcebytestr(e.strerror)
+        )
+    finally:
+        if wlock:
+            wlock.release()

tests/test-share-safe.t

@@ -479,8 +479,63 b' Make sure existing shares still works'
   |
   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]
+
+
+Testing automatic upgrade of shares when config is set
+
+  $ hg debugupgraderepo -q --run --config format.exp-share-safe=True
+  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
+  $ 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
+  
+
+Check that if lock is taken, upgrade fails but read operation are successful
+  $ touch ../nss-share/.hg/wlock
+  $ hg log -GT "{node}: {desc}\n" -R ../nss-share --config experimental.sharesafe-auto-upgrade-shares=true
+  failed to upgrade share, got error: Lock held
+  @  f63db81e6dde1d9c78814167f77fb1fb49283f4f: added bar
+  |
+  o  f3ba8b99bb6f897c87bbc1c07b75c6ddf43a4f77: added foo
+  
+  $ rm ../nss-share/.hg/wlock
+  $ hg log -GT "{node}: {desc}\n" -R ../nss-share --config experimental.sharesafe-auto-upgrade-shares=true
+  repository upgraded to use share-safe mode
+  @  f63db81e6dde1d9c78814167f77fb1fb49283f4f: added bar
+  |
+  o  f3ba8b99bb6f897c87bbc1c07b75c6ddf43a4f77: added foo
+  
+
+Test that unshare works
+
+  $ hg unshare -R ../nss-share
+  $ hg log -GT "{node}: {desc}\n" -R ../nss-share
+  @  f63db81e6dde1d9c78814167f77fb1fb49283f4f: added bar
+  |
+  o  f3ba8b99bb6f897c87bbc1c07b75c6ddf43a4f77: added foo
+