amend: add noise in extra to avoid creating obsolescence cycle (issue3664)

Obsolescence cycle are bad and should be avoided as much as possible. The
current amend implemented touch changeset meta data as few as possible. This
make is easy for amend to result in the same node than a precursors. We add some
deterministic noise in extra to avoid this. In practice, the hex of the amended
changeset is stored in 'amend_source' extra key.

mercurial/cmdutil.py

@@ -11,6 +11,7 b' import os, sys, errno, re, tempfile'
 import util, scmutil, templater, patch, error, templatekw, revlog, copies
 import match as matchmod
 import subrepo, context, repair, bookmarks, graphmod, revset, phases, obsolete
+import changelog
 import lock as lockmod
 
 def parsealiases(cmd):
@@ -1696,6 +1697,9 b' def amend(ui, repo, commitfunc, old, ext'
             if not message:
                 message = old.description()
 
+            pureextra = extra.copy()
+            extra['amend_source'] = old.hex()
+
             new = context.memctx(repo,
                                  parents=[base.node(), nullid],
                                  text=message,
@@ -1705,6 +1709,19 b' def amend(ui, repo, commitfunc, old, ext'
                                  date=date,
                                  extra=extra)
             new._text = commitforceeditor(repo, new, [])
+
+            newdesc =  changelog.stripdesc(new.description())
+            if ((not node)
+                and newdesc == old.description()
+                and user == old.user()
+                and date == old.date()
+                and pureextra == old.extra()):
+                # nothing changed. continuing here would create a new node
+                # anyway because of the amend_source noise.
+                #
+                # This not what we expect from amend.
+                return old.node()
+
             ph = repo.ui.config('phases', 'new-commit', phases.draft)
             try:
                 repo.ui.setconfig('phases', 'new-commit', old.phase())

tests/test-commit-amend.t

@@ -32,12 +32,12 b' Amending changeset with changes in worki'
 
   $ echo a >> a
   $ hg ci --amend -m 'amend base1'
-  pretxncommit 9cd25b479c51be2f4ed2c38e7abdf7ce67d8e0dc
-  9cd25b479c51 tip
+  pretxncommit 43f1ba15f28a50abf0aae529cf8a16bfced7b149
+  43f1ba15f28a tip
   saved backup bundle to $TESTTMP/.hg/strip-backup/489edb5b847d-amend-backup.hg (glob)
   $ echo 'pretxncommit.foo = ' >> $HGRCPATH
   $ hg diff -c .
-  diff -r ad120869acf0 -r 9cd25b479c51 a
+  diff -r ad120869acf0 -r 43f1ba15f28a a
   --- a/a	Thu Jan 01 00:00:00 1970 +0000
   +++ b/a	Thu Jan 01 00:00:00 1970 +0000
   @@ -1,1 +1,3 @@
@@ -45,7 +45,7 b' Amending changeset with changes in worki'
   +a
   +a
   $ hg log
-  changeset:   1:9cd25b479c51
+  changeset:   1:43f1ba15f28a
   tag:         tip
   user:        test
   date:        Thu Jan 01 00:00:00 1970 +0000
@@ -62,36 +62,36 b' Add new file:'
   $ echo b > b
   $ hg ci --amend -Am 'amend base1 new file'
   adding b
-  saved backup bundle to $TESTTMP/.hg/strip-backup/9cd25b479c51-amend-backup.hg (glob)
+  saved backup bundle to $TESTTMP/.hg/strip-backup/43f1ba15f28a-amend-backup.hg (glob)
 
 Remove file that was added in amended commit:
 
   $ hg rm b
   $ hg ci --amend -m 'amend base1 remove new file'
-  saved backup bundle to $TESTTMP/.hg/strip-backup/e2bb3ecffd2f-amend-backup.hg (glob)
+  saved backup bundle to $TESTTMP/.hg/strip-backup/b8e3cb2b3882-amend-backup.hg (glob)
 
   $ hg cat b
-  b: no such file in rev 664a9b2d60cd
+  b: no such file in rev 74609c7f506e
   [1]
 
 No changes, just a different message:
 
   $ hg ci -v --amend -m 'no changes, new message'
-  amending changeset 664a9b2d60cd
-  copying changeset 664a9b2d60cd to ad120869acf0
+  amending changeset 74609c7f506e
+  copying changeset 74609c7f506e to ad120869acf0
   a
-  stripping amended changeset 664a9b2d60cd
+  stripping amended changeset 74609c7f506e
   1 changesets found
-  saved backup bundle to $TESTTMP/.hg/strip-backup/664a9b2d60cd-amend-backup.hg (glob)
+  saved backup bundle to $TESTTMP/.hg/strip-backup/74609c7f506e-amend-backup.hg (glob)
   1 changesets found
   adding branch
   adding changesets
   adding manifests
   adding file changes
   added 1 changesets with 1 changes to 1 files
-  committed changeset 1:ea6e356ff2ad
+  committed changeset 1:1cd866679df8
   $ hg diff -c .
-  diff -r ad120869acf0 -r ea6e356ff2ad a
+  diff -r ad120869acf0 -r 1cd866679df8 a
   --- a/a	Thu Jan 01 00:00:00 1970 +0000
   +++ b/a	Thu Jan 01 00:00:00 1970 +0000
   @@ -1,1 +1,3 @@
@@ -99,7 +99,7 b' No changes, just a different message:'
   +a
   +a
   $ hg log
-  changeset:   1:ea6e356ff2ad
+  changeset:   1:1cd866679df8
   tag:         tip
   user:        test
   date:        Thu Jan 01 00:00:00 1970 +0000
@@ -119,12 +119,12 b' Disable default date on commit so when -'
 Test -u/-d:
 
   $ hg ci --amend -u foo -d '1 0'
-  saved backup bundle to $TESTTMP/.hg/strip-backup/ea6e356ff2ad-amend-backup.hg (glob)
+  saved backup bundle to $TESTTMP/.hg/strip-backup/1cd866679df8-amend-backup.hg (glob)
   $ echo a >> a
   $ hg ci --amend -u foo -d '1 0'
-  saved backup bundle to $TESTTMP/.hg/strip-backup/377b91ce8b56-amend-backup.hg (glob)
+  saved backup bundle to $TESTTMP/.hg/strip-backup/780e6f23e03d-amend-backup.hg (glob)
   $ hg log -r .
-  changeset:   1:2c94e4a5756f
+  changeset:   1:5f357c7560ab
   tag:         tip
   user:        foo
   date:        Thu Jan 01 00:00:01 1970 +0000
@@ -139,8 +139,8 b' Open editor with old commit message if a'
   > echo "another precious commit message" > "$1"
   > __EOF__
   $ HGEDITOR="\"sh\" \"`pwd`/editor.sh\"" hg commit --amend -v
-  amending changeset 2c94e4a5756f
-  copying changeset 2c94e4a5756f to ad120869acf0
+  amending changeset 5f357c7560ab
+  copying changeset 5f357c7560ab to ad120869acf0
   no changes, new message
   
   
@@ -151,24 +151,24 b' Open editor with old commit message if a'
   HG: branch 'default'
   HG: changed a
   a
-  stripping amended changeset 2c94e4a5756f
+  stripping amended changeset 5f357c7560ab
   1 changesets found
-  saved backup bundle to $TESTTMP/.hg/strip-backup/2c94e4a5756f-amend-backup.hg (glob)
+  saved backup bundle to $TESTTMP/.hg/strip-backup/5f357c7560ab-amend-backup.hg (glob)
   1 changesets found
   adding branch
   adding changesets
   adding manifests
   adding file changes
   added 1 changesets with 1 changes to 1 files
-  committed changeset 1:ffb49186f961
+  committed changeset 1:7ab3bf440b54
 
 Same, but with changes in working dir (different code path):
 
   $ echo a >> a
   $ HGEDITOR="\"sh\" \"`pwd`/editor.sh\"" hg commit --amend -v
-  amending changeset ffb49186f961
+  amending changeset 7ab3bf440b54
   a
-  copying changeset a4f8a65b7c6a to ad120869acf0
+  copying changeset a0ea9b1a4c8c to ad120869acf0
   another precious commit message
   
   
@@ -179,21 +179,21 b' Same, but with changes in working dir (d'
   HG: branch 'default'
   HG: changed a
   a
-  stripping intermediate changeset a4f8a65b7c6a
-  stripping amended changeset ffb49186f961
+  stripping intermediate changeset a0ea9b1a4c8c
+  stripping amended changeset 7ab3bf440b54
   2 changesets found
-  saved backup bundle to $TESTTMP/.hg/strip-backup/ffb49186f961-amend-backup.hg (glob)
+  saved backup bundle to $TESTTMP/.hg/strip-backup/7ab3bf440b54-amend-backup.hg (glob)
   1 changesets found
   adding branch
   adding changesets
   adding manifests
   adding file changes
   added 1 changesets with 1 changes to 1 files
-  committed changeset 1:fb6cca43446f
+  committed changeset 1:ea22a388757c
 
   $ rm editor.sh
   $ hg log -r .
-  changeset:   1:fb6cca43446f
+  changeset:   1:ea22a388757c
   tag:         tip
   user:        foo
   date:        Thu Jan 01 00:00:01 1970 +0000
@@ -205,16 +205,16 b' Moving bookmarks, preserve active bookma'
   $ hg book book1
   $ hg book book2
   $ hg ci --amend -m 'move bookmarks'
-  saved backup bundle to $TESTTMP/.hg/strip-backup/fb6cca43446f-amend-backup.hg (glob)
+  saved backup bundle to $TESTTMP/.hg/strip-backup/ea22a388757c-amend-backup.hg (glob)
   $ hg book
-     book1                     1:0cf1c7a51bcf
-   * book2                     1:0cf1c7a51bcf
+     book1                     1:6cec5aa930e2
+   * book2                     1:6cec5aa930e2
   $ echo a >> a
   $ hg ci --amend -m 'move bookmarks'
-  saved backup bundle to $TESTTMP/.hg/strip-backup/0cf1c7a51bcf-amend-backup.hg (glob)
+  saved backup bundle to $TESTTMP/.hg/strip-backup/6cec5aa930e2-amend-backup.hg (glob)
   $ hg book
-     book1                     1:7344472bd951
-   * book2                     1:7344472bd951
+     book1                     1:48bb6e53a15f
+   * book2                     1:48bb6e53a15f
 
   $ echo '[defaults]' >> $HGRCPATH
   $ echo "commit=-d '0 0'" >> $HGRCPATH
@@ -230,9 +230,9 b' Moving branches:'
   marked working directory as branch default
   (branches are permanent and global, did you want a bookmark?)
   $ hg ci --amend -m 'back to default'
-  saved backup bundle to $TESTTMP/.hg/strip-backup/1661ca36a2db-amend-backup.hg (glob)
+  saved backup bundle to $TESTTMP/.hg/strip-backup/8ac881fbf49d-amend-backup.hg (glob)
   $ hg branches
-  default                        2:f24ee5961967
+  default                        2:ce12b0b57d46
 
 Close branch:
 
@@ -255,9 +255,9 b' Same thing, different code path:'
   reopening closed branch head 4
   $ echo b >> b
   $ hg ci --amend --close-branch
-  saved backup bundle to $TESTTMP/.hg/strip-backup/5e302dcc12b8-amend-backup.hg (glob)
+  saved backup bundle to $TESTTMP/.hg/strip-backup/027371728205-amend-backup.hg (glob)
   $ hg branches
-  default                        2:f24ee5961967
+  default                        2:ce12b0b57d46
 
 Refuse to amend merges:
 
@@ -279,7 +279,7 b' Follow copies/renames:'
   $ hg ci -m 'b -> c'
   $ hg mv c d
   $ hg ci --amend -m 'b -> d'
-  saved backup bundle to $TESTTMP/.hg/strip-backup/9c207120aa98-amend-backup.hg (glob)
+  saved backup bundle to $TESTTMP/.hg/strip-backup/b8c6eac7f12e-amend-backup.hg (glob)
   $ hg st --rev '.^' --copies d
   A d
     b
@@ -287,7 +287,7 b' Follow copies/renames:'
   $ hg ci -m 'e = d'
   $ hg cp e f
   $ hg ci --amend -m 'f = d'
-  saved backup bundle to $TESTTMP/.hg/strip-backup/fda2b3b27b22-amend-backup.hg (glob)
+  saved backup bundle to $TESTTMP/.hg/strip-backup/7f9761d65613-amend-backup.hg (glob)
   $ hg st --rev '.^' --copies f
   A f
     d
@@ -298,7 +298,7 b' Follow copies/renames:'
   $ hg cp a f
   $ mv f.orig f
   $ hg ci --amend -m replacef
-  saved backup bundle to $TESTTMP/.hg/strip-backup/20a7413547f9-amend-backup.hg (glob)
+  saved backup bundle to $TESTTMP/.hg/strip-backup/9e8c5f7e3d95-amend-backup.hg (glob)
   $ hg st --change . --copies
   $ hg log -r . --template "{file_copies}\n"
   
@@ -310,7 +310,7 b' Move added file (issue3410):'
   adding g
   $ hg mv g h
   $ hg ci --amend
-  saved backup bundle to $TESTTMP/.hg/strip-backup/5daa77a5d616-amend-backup.hg (glob)
+  saved backup bundle to $TESTTMP/.hg/strip-backup/24aa8eacce2b-amend-backup.hg (glob)
   $ hg st --change . --copies h
   A h
   $ hg log -r . --template "{file_copies}\n"
@@ -330,11 +330,11 b' Preserve extra dict (issue3430):'
   $ echo a >> a
   $ hg ci -ma
   $ hg ci --amend -m "a'"
-  saved backup bundle to $TESTTMP/.hg/strip-backup/167f8e3031df-amend-backup.hg (glob)
+  saved backup bundle to $TESTTMP/.hg/strip-backup/3837aa2a2fdb-amend-backup.hg (glob)
   $ hg log -r . --template "{branch}\n"
   a
   $ hg ci --amend -m "a''"
-  saved backup bundle to $TESTTMP/.hg/strip-backup/ceac1a44c806-amend-backup.hg (glob)
+  saved backup bundle to $TESTTMP/.hg/strip-backup/c05c06be7514-amend-backup.hg (glob)
   $ hg log -r . --template "{branch}\n"
   a
 
@@ -351,8 +351,9 b" first graft something so there's an addi"
   $ hg graft 12
   grafting revision 12
   $ hg ci --amend -m 'graft amend'
-  saved backup bundle to $TESTTMP/.hg/strip-backup/18a5124daf7a-amend-backup.hg (glob)
+  saved backup bundle to $TESTTMP/.hg/strip-backup/bd010aea3f39-amend-backup.hg (glob)
   $ hg log -r . --debug | grep extra
+  extra:       amend_source=bd010aea3f39f3fb2a2f884b9ccb0471cd77398e
   extra:       branch=a
   extra:       source=2647734878ef0236dda712fae9c1651cf694ea8a
 
@@ -391,26 +392,26 b' Amend with no files changes'
   $ hg id -n
   14
   $ hg log -Gl 3 --style=compact
-  @  14[tip]:11   43df5a5434ad   1970-01-01 00:00 +0000   test
+  @  14[tip]:11   b650e6ee8614   1970-01-01 00:00 +0000   test
   |    babar
   |
   | o  12:0   2647734878ef   1970-01-01 00:00 +0000   test
   | |    fork
   | |
-  o |  11   7e09f708a0e9   1970-01-01 00:00 +0000   test
+  o |  11   3334b7925910   1970-01-01 00:00 +0000   test
   | |    a''
   | |
   $ hg log -Gl 4 --hidden --style=compact
-  @  14[tip]:11   43df5a5434ad   1970-01-01 00:00 +0000   test
+  @  14[tip]:11   b650e6ee8614   1970-01-01 00:00 +0000   test
   |    babar
   |
-  | x  13:11   175fafee6f44   1970-01-01 00:00 +0000   test
+  | x  13:11   68ff8ff97044   1970-01-01 00:00 +0000   test
   |/     amend for phase
   |
   | o  12:0   2647734878ef   1970-01-01 00:00 +0000   test
   | |    fork
   | |
-  o |  11   7e09f708a0e9   1970-01-01 00:00 +0000   test
+  o |  11   3334b7925910   1970-01-01 00:00 +0000   test
   | |    a''
   | |
 
@@ -422,23 +423,34 b' ride of)'
   $ echo 'babar' >> a
   $ hg commit --amend
   $ hg log -Gl 6 --hidden --style=compact
-  @  16[tip]:11   31e0a4a1b04a   1970-01-01 00:00 +0000   test
+  @  16[tip]:11   9f9e9bccf56c   1970-01-01 00:00 +0000   test
   |    babar
   |
-  | x  15   053c696ada75   1970-01-01 00:00 +0000   test
-  | |    temporary amend commit for 43df5a5434ad
+  | x  15   90fef497c56f   1970-01-01 00:00 +0000   test
+  | |    temporary amend commit for b650e6ee8614
   | |
-  | x  14:11   43df5a5434ad   1970-01-01 00:00 +0000   test
+  | x  14:11   b650e6ee8614   1970-01-01 00:00 +0000   test
   |/     babar
   |
-  | x  13:11   175fafee6f44   1970-01-01 00:00 +0000   test
+  | x  13:11   68ff8ff97044   1970-01-01 00:00 +0000   test
   |/     amend for phase
   |
   | o  12:0   2647734878ef   1970-01-01 00:00 +0000   test
   | |    fork
   | |
-  o |  11   7e09f708a0e9   1970-01-01 00:00 +0000   test
+  o |  11   3334b7925910   1970-01-01 00:00 +0000   test
   | |    a''
   | |
 
 
+Test that amend does not make it easy to create obsoletescence cycle
+---------------------------------------------------------------------
+
+
+  $ hg id -r 14
+  b650e6ee8614 (a)
+  $ hg revert -ar 14
+  reverting a
+  $ hg commit --amend
+  $ hg id
+  b99e5df575f7 (a) tip

tests/test-keyword.t

@@ -509,9 +509,9 b' amend'
   $ hg --debug commit --amend -d '15 1' -m 'amend without changes' | grep keywords
   overwriting a expanding keywords
   $ hg -q id
-  577e60613a88
+  67d8c481a6be
   $ head -1 a
-  expand $Id: a,v 577e60613a88 1970/01/01 00:00:15 test $
+  expand $Id: a,v 67d8c481a6be 1970/01/01 00:00:15 test $
 
   $ hg -q strip -n tip