$ cat >> $HGRCPATH <<EOF

  > [web]

  > push_ssl = false

  > allow_push = *

  > [phases]

  > publish=False

  > [alias]

  > odiff=diff --rev 'limit(obsparents(.),1)' --rev .

  > [extensions]

  > EOF

  $ mkcommit() {

  >    echo "$1" > "$1"

  >    hg add "$1"

  >    hg ci -m "add $1"

  > }

create commit

  $ hg init repo

  $ cd repo

  $ mkcommit a

  $ mkcommit b

  $ hg up -q 0

  $ mkcommit c

  created new head

forge old style relation files

  $ hg log -r 2 --template='{node} ' > .hg/obsolete-relations

  $ hg log -r 1 --template='{node}' >> .hg/obsolete-relations

enable the extensions

  $ echo "obsolete=$(echo $(dirname $TESTDIR))/hgext3rd/evolve/legacy.py" >> $HGRCPATH

  $ hg log -G

  abort: old format of obsolete marker detected!

  run `hg debugconvertobsolete` once.

  [255]

  $ hg debugconvertobsolete --traceback

  1 obsolete marker converted

  $ hg log -G

  @  changeset:   2:d67cd0334eee

  |  tag:         tip

  |  parent:      0:1f0dee641bb7

  |  user:        test

  |  date:        Thu Jan 01 00:00:00 1970 +0000

  |  summary:     add c

  |

  o  changeset:   0:1f0dee641bb7

     user:        test

     date:        Thu Jan 01 00:00:00 1970 +0000

     summary:     add a

  $ hg debugobsolete

  7c3bad9141dcb46ff89abf5f61856facd56e476c d67cd0334eeecfded222fed9009f0db4beb57585 0 (*) {'user': 'test'} (glob)

  $ hg debugconvertobsolete

  nothing to do

  0 obsolete marker converted

Convert json

  $ cat > .hg/store/obsoletemarkers << EOF

  > [

  >     {

  >         "reason": "import from older format.", 

  >         "subjects": [

  >             "3218406b50ed13480765e7c260669620f37fba6e"

  >         ], 

  >         "user": "Pierre-Yves David <pierre-yves.david@ens-lyon.org>", 

  >         "date": [

  >             1336503323.9768269, 

  >             -7200

  >         ], 

  >         "object": "3e03d82708d4da97a92158558dd13386d8f09ad5", 

  >         "id": "4743f676eaf3923cb98c921ee06b2e91052c365b"

  >     }, 

  >     {

  >         "reason": "import from older format.", 

  >         "user": "Pierre-Yves David <pierre-yves.david@logilab.fr>", 

  >         "date": [

  >             1336557472.7875929, 

  >             -7200

  >         ], 

  >         "object": "5c722672795c3a2cb94d0cc9a821c394c1475f87", 

  >         "id": "1fd90a84b7225d2e3062b7e1b3100aa2e060fc72"

  >     }, 

  >     {

  >         "reason": "import from older format.", 

  >         "subjects": [

  >             "0000000000000000000000000000000000000000"

  >         ], 

  >         "user": "Pierre-Yves David <pierre-yves.david@logilab.fr>", 

  >         "date": [

  >             1336557472.784307, 

  >             -7200

  >         ], 

  >         "object": "2c3784e102bb34ccc93862af5bd6d609ee30c577", 

  >         "id": "7d940c5ee1f886c8a6c0d805b43e522cb3ef7a15"

  >     }

  > ]

  > EOF

  $ hg log -G

  abort: old format of obsolete marker detected!

  run `hg debugconvertobsolete` once.

  [255]

  $ hg debugconvertobsolete --traceback

  3 obsolete marker converted

  $ hg debugobsolete

  7c3bad9141dcb46ff89abf5f61856facd56e476c d67cd0334eeecfded222fed9009f0db4beb57585 0 (*) {'user': 'test'} (glob)

  3e03d82708d4da97a92158558dd13386d8f09ad5 3218406b50ed13480765e7c260669620f37fba6e 0 (Tue May 08 20:55:23 2012 +0200) {'user': 'Pierre-Yves David <pierre-yves.david@ens-lyon.org>'}

  5c722672795c3a2cb94d0cc9a821c394c1475f87 0 (Wed May 09 11:57:52 2012 +0200) {'user': 'Pierre-Yves David <pierre-yves.david@logilab.fr>'}

  2c3784e102bb34ccc93862af5bd6d609ee30c577 0 (Wed May 09 11:57:52 2012 +0200) {'user': 'Pierre-Yves David <pierre-yves.david@logilab.fr>'}