rewriting: add an option for rewrite commands to use the archived phase

Using the archived phase for cleanup provide the same effect than stripping,
but in a faster, append-only way.

We keep the feature experimental for now until it gets a bit more testing.

mercurial/configitems.py

@@ -470,6 +470,9 b" coreconfigitem('experimental', 'bundleco"
 coreconfigitem('experimental', 'changegroup3',
     default=False,
 )
+coreconfigitem('experimental', 'cleanup-as-archived',
+    default=False,
+)
 coreconfigitem('experimental', 'clientcompressionengines',
     default=list,
 )

mercurial/scmutil.py

@@ -1016,6 +1016,7 b' def cleanupnodes(repo, replacements, ope'
         for phase, nodes in toadvance.items():
             phases.advanceboundary(repo, tr, phase, nodes)
 
+        mayusearchived = repo.ui.config('experimental', 'cleanup-as-archived')
         # Obsolete or strip nodes
         if obsolete.isenabled(repo, obsolete.createmarkersopt):
             # If a node is already obsoleted, and we want to obsolete it
@@ -1033,6 +1034,17 b' def cleanupnodes(repo, replacements, ope'
             if rels:
                 obsolete.createmarkers(repo, rels, operation=operation,
                                        metadata=metadata)
+        elif phases.supportinternal(repo) and mayusearchived:
+            # this assume we do not have "unstable" nodes above the cleaned ones
+            allreplaced = set()
+            for ns in replacements.keys():
+                allreplaced.update(ns)
+            if backup:
+                from . import repair # avoid import cycle
+                node = min(allreplaced, key=repo.changelog.rev)
+                repair.backupbundle(repo, allreplaced, allreplaced, node,
+                                    operation)
+            phases.retractboundary(repo, tr, phases.archived, allreplaced)
         else:
             from . import repair # avoid import cycle
             tostrip = list(n for ns in replacements for n in ns)

tests/test-phase-archived.t

@@ -75,3 +75,69 b' Test that bundle can unarchive a changes'
      date:        Thu Jan 01 00:00:00 1970 +0000
      summary:     root
   
+
+Test that history rewriting command can use the archived phase when allowed to
+------------------------------------------------------------------------------
+
+  $ hg up 'desc(unbundletesting)'
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ echo bar >> a
+  $ hg commit --amend --config experimental.cleanup-as-archived=yes
+  $ hg log -G
+  @  changeset:   2:d1e73e428f29
+  |  tag:         tip
+  |  parent:      0:c1863a3840c6
+  |  user:        test
+  |  date:        Thu Jan 01 00:00:00 1970 +0000
+  |  summary:     unbundletesting
+  |
+  o  changeset:   0:c1863a3840c6
+     user:        test
+     date:        Thu Jan 01 00:00:00 1970 +0000
+     summary:     root
+  
+  $ hg log -G --hidden
+  @  changeset:   2:d1e73e428f29
+  |  tag:         tip
+  |  parent:      0:c1863a3840c6
+  |  user:        test
+  |  date:        Thu Jan 01 00:00:00 1970 +0000
+  |  summary:     unbundletesting
+  |
+  | o  changeset:   1:883aadbbf309
+  |/   user:        test
+  |    date:        Thu Jan 01 00:00:00 1970 +0000
+  |    summary:     unbundletesting
+  |
+  o  changeset:   0:c1863a3840c6
+     user:        test
+     date:        Thu Jan 01 00:00:00 1970 +0000
+     summary:     root
+  
+  $ ls -1 .hg/strip-backup/
+  883aadbbf309-efc55adc-amend.hg
+  883aadbbf309-efc55adc-backup.hg
+  $ hg unbundle .hg/strip-backup/883aadbbf309*amend.hg
+  adding changesets
+  adding manifests
+  adding file changes
+  added 0 changesets with 0 changes to 1 files
+  (run 'hg update' to get a working copy)
+  $ hg log -G
+  @  changeset:   2:d1e73e428f29
+  |  tag:         tip
+  |  parent:      0:c1863a3840c6
+  |  user:        test
+  |  date:        Thu Jan 01 00:00:00 1970 +0000
+  |  summary:     unbundletesting
+  |
+  | o  changeset:   1:883aadbbf309
+  |/   user:        test
+  |    date:        Thu Jan 01 00:00:00 1970 +0000
+  |    summary:     unbundletesting
+  |
+  o  changeset:   0:c1863a3840c6
+     user:        test
+     date:        Thu Jan 01 00:00:00 1970 +0000
+     summary:     root
+