[PATCH 05 of 10] repair: obtain and validate requirements for upgraded repo

[Gregory Szorc]

# HG changeset patch
# User Gregory Szorc <gregory.szorc at gmail.com>
# Date 1478394961 25200
#      Sat Nov 05 18:16:01 2016 -0700
# Node ID b768004ef2db9c2e6dd267997e9e0c011f1b732a
# Parent  7518e68e2f8276e85fb68174b3055a9dd16c665d
repair: obtain and validate requirements for upgraded repo

Not all existing repositories can be upgraded. Not all requirements
are supported in new repositories. Some transitions between
repository requirements (notably removing a requirement) are not
supported.

This patch adds code for validating that the requirements transition
for repository upgrades is acceptable and aborts if it isn't.
Functionality is split into various functions to give extensions an
opportunity to monkeypatch.

diff --git a/mercurial/repair.py b/mercurial/repair.py
--- a/mercurial/repair.py
+++ b/mercurial/repair.py
@@ -401,6 +401,85 @@ def upgradefinddeficiencies(repo):
 
     return l, actions
 
+def upgradesupporteddestrequirements(repo):
+    """Obtain requirements that upgrade supports in the destination.
+
+    Extensions should monkeypatch this to add their custom requirements.
+    """
+    return set([
+        'dotencode',
+        'fncache',
+        'generaldelta',
+        'manifestv2',
+        'revlogv1',
+        'store',
+        'treemanifest',
+    ])
+
+def upgraderequiredsourcerequirements(repo):
+    """Obtain requirements that must be present in the source repository."""
+    return set([
+        'revlogv1',
+        'store',
+    ])
+
+def upgradeallowednewrequirements(repo):
+    """Obtain requirements that can be added to a repository.
+
+    This is used to disallow proposed requirements from being added when
+    they weren't present before.
+
+    We use a whitelist of allowed requirement additions instead of a
+    blacklist of known bad additions because the whitelist approach is
+    safer and will prevent future, unknown requirements from accidentally
+    being added.
+    """
+    return set([
+        'dotencode',
+        'fncache',
+        'generaldelta',
+    ])
+
+def upgradereporequirements(repo):
+    """Obtain and validate requirements for repository after upgrade.
+
+    Should raise ``Abort`` if existing or new requirements aren't sufficient.
+    """
+    # Avoid cycle: cmdutil -> repair -> localrepo -> cmdutil
+    from . import localrepo
+
+    existing = repo.requirements
+
+    missingreqs = upgraderequiredsourcerequirements(repo) - existing
+    if missingreqs:
+        raise error.Abort(_('cannot upgrade repository; requirement '
+                            'missing: %s') % ', '.join(sorted(missingreqs)))
+
+    createreqs = localrepo.newreporequirements(repo)
+
+    # This might be overly restrictive. It is definitely safer to enforce this
+    # as it prevents unwanted deletion of requirements.
+    removedreqs = existing - createreqs
+    if removedreqs:
+        raise error.Abort(_('cannot upgrade repository; requirement would '
+                            'be removed: %s') % ', '.join(sorted(removedreqs)))
+
+    unsupportedreqs = createreqs - upgradesupporteddestrequirements(repo)
+    if unsupportedreqs:
+        raise error.Abort(_('cannot upgrade repository; new requirement not '
+                           'supported: %s') %
+                          ', '.join(sorted(unsupportedreqs)))
+
+    # Alternatively, we could silently remove the disallowed requirement
+    # instead of aborting.
+    noaddreqs = createreqs - existing - upgradeallowednewrequirements(repo)
+    if noaddreqs:
+        raise error.Abort(_('cannot upgrade repository; proposed new '
+                            'requirement cannot be added: %s') %
+                          ', '.join(sorted(noaddreqs)))
+
+    return createreqs
+
 def upgraderepo(ui, repo, dryrun=False):
     """Upgrade a repository in place."""
     repo = repo.unfiltered()
@@ -414,3 +493,17 @@ def upgraderepo(ui, repo, dryrun=False):
             ui.write('* %s\n' % d)
     else:
         ui.write(_('no obvious deficiencies found in existing repository\n'))
+
+    ui.write(_('\n'))
+    ui.write(_('checking repository requirements...\n'))
+
+    newreqs = upgradereporequirements(repo)
+    # We don't drop requirements.
+    assert not len(repo.requirements - newreqs)
+
+    ui.write(_('preserving repository requirements: %s\n') %
+             ', '.join(sorted(repo.requirements & newreqs)))
+    if newreqs - repo.requirements:
+        ui.write(_('adding repository requirements: %s\n') %
+                 ', '.join(sorted(newreqs - repo.requirements)))
+
diff --git a/tests/test-upgrade-repo.t b/tests/test-upgrade-repo.t
--- a/tests/test-upgrade-repo.t
+++ b/tests/test-upgrade-repo.t
@@ -2,6 +2,9 @@
   $ cd empty
   $ hg debugupgraderepo
   no obvious deficiencies found in existing repository
+  
+  checking repository requirements...
+  preserving repository requirements: dotencode, fncache, generaldelta, revlogv1, store
 
 Various sub-optimal detections work
 
@@ -16,3 +19,57 @@ Various sub-optimal detections work
   * not using fncache; long and reserved filenames may not work correctly
   * not using dotencode; filenames beginning with a period or space may not work correctly
   * not using generaldelta storage; repository is larger and slower than it could be, pulling from generaldelta repositories will be slow
+  
+  checking repository requirements...
+  preserving repository requirements: revlogv1, store
+  adding repository requirements: dotencode, fncache, generaldelta
+
+  $ cd ..
+
+store and revlogv1 are required in source
+
+  $ hg init no-revlogv1
+  $ cat > no-revlogv1/.hg/requires << EOF
+  > dotencode
+  > fncache
+  > generaldelta
+  > store
+  > EOF
+
+  $ hg -R no-revlogv1 debugupgraderepo
+  no obvious deficiencies found in existing repository
+  
+  checking repository requirements...
+  abort: cannot upgrade repository; requirement missing: revlogv1
+  [255]
+
+  $ hg --config format.usestore=false init no-store
+  $ hg -R no-store debugupgraderepo
+  the following deficiencies with the existing repository have been identified:
+  
+  * not using fncache; long and reserved filenames may not work correctly
+  * not using dotencode; filenames beginning with a period or space may not work correctly
+  
+  checking repository requirements...
+  abort: cannot upgrade repository; requirement missing: store
+  [255]
+
+Cannot drop requirement during upgrade
+
+  $ hg --config experimental.treemanifest=true init treemanifest-drop
+  $ hg -R treemanifest-drop debugupgraderepo
+  no obvious deficiencies found in existing repository
+  
+  checking repository requirements...
+  abort: cannot upgrade repository; requirement would be removed: treemanifest
+  [255]
+
+Cannot add specific requirements during upgrade
+
+  $ hg init disallowaddedreq
+  $ hg -R disallowaddedreq --config experimental.treemanifest=true debugupgraderepo
+  no obvious deficiencies found in existing repository
+  
+  checking repository requirements...
+  abort: cannot upgrade repository; proposed new requirement cannot be added: treemanifest
+  [255]