test-bundle2: also test the argument of the changegroup hook

We also track execution of the changegroup hook. The important information here
is to make sure the information that the transaction was processing a bundle2 is passed to
hook. This will let most hooks disable themselves while waiting for the hook
concluding bundle2 processing (the one we discovered to be not called for
pull in the previous changesets).

tests/test-bundle2-exchange.t

@@ -26,6 +26,7 b' enable obsolescence'
   > [phases]
   > publish=False
   > [hooks]
+  > changegroup = sh -c  "HG_LOCAL= HG_NODE= HG_TAG= python \"$TESTDIR/printenv.py\" changegroup"
   > b2x-transactionclose = sh -c  "HG_LOCAL= HG_NODE= HG_TAG= python \"$TESTDIR/printenv.py\" b2x-transactionclose"
   > EOF
 
@@ -42,6 +43,7 b' The extension requires a repo (currently'
   adding manifests
   adding file changes
   added 8 changesets with 7 changes to 7 files (+3 heads)
+  changegroup hook: HG_SOURCE=unbundle HG_URL=bundle:*/tests/bundles/rebase.hg (glob)
   (run 'hg heads' to see heads, 'hg merge' to merge)
 
   $ cd ..
@@ -63,6 +65,7 b' clone --pull'
   adding file changes
   added 2 changesets with 2 changes to 2 files
   1 new obsolescence markers
+  changegroup hook: HG_NEW_OBSMARKERS=1 HG_SOURCE=bundle2 HG_URL=bundle2
   updating to branch default
   2 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ hg -R other log -G
@@ -84,6 +87,7 b' pull'
   adding file changes
   added 1 changesets with 1 changes to 1 files (+1 heads)
   1 new obsolescence markers
+  changegroup hook: HG_NEW_OBSMARKERS=1 HG_SOURCE=bundle2 HG_URL=bundle2
   (run 'hg heads' to see heads, 'hg merge' to merge)
   $ hg -R other log -G
   o  2:24b6387c8c8c draft Nicolas Dumazet <[e-mail]>  F
@@ -155,6 +159,7 b' push'
   pushing to other
   searching for changes
   b2x-transactionclose hook: HG_BUNDLE2-EXP=1 HG_NEW_OBSMARKERS=1 HG_SOURCE=push HG_URL=push
+  changegroup hook: HG_BUNDLE2-EXP=1 HG_NEW_OBSMARKERS=1 HG_SOURCE=bundle2 HG_URL=bundle2
   remote: adding changesets
   remote: adding manifests
   remote: adding file changes
@@ -186,6 +191,7 b' pull over ssh'
   added 1 changesets with 1 changes to 1 files (+1 heads)
   1 new obsolescence markers
   updating bookmark book_02de
+  changegroup hook: HG_NEW_OBSMARKERS=1 HG_SOURCE=bundle2 HG_URL=bundle2
   (run 'hg heads' to see heads, 'hg merge' to merge)
   $ hg -R other debugobsolete
   1111111111111111111111111111111111111111 9520eea781bcca16c1e15acc0ba14335a0e8e5ba 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
@@ -207,6 +213,7 b' pull over http'
   added 1 changesets with 1 changes to 1 files (+1 heads)
   1 new obsolescence markers
   updating bookmark book_42cc
+  changegroup hook: HG_NEW_OBSMARKERS=1 HG_SOURCE=bundle2 HG_URL=bundle2
   (run 'hg heads .' to see heads, 'hg merge' to merge)
   $ cat main-error.log
   $ hg -R other debugobsolete
@@ -228,6 +235,7 b' push over ssh'
   remote: 1 new obsolescence markers
   updating bookmark book_5fdd
   remote: b2x-transactionclose hook: HG_BUNDLE2-EXP=1 HG_NEW_OBSMARKERS=1 HG_SOURCE=serve HG_URL=remote:ssh:127.0.0.1
+  remote: changegroup hook: HG_BUNDLE2-EXP=1 HG_NEW_OBSMARKERS=1 HG_SOURCE=bundle2 HG_URL=bundle2
   $ hg -R other log -G
   o  6:5fddd98957c8 draft Nicolas Dumazet <[e-mail]> book_5fdd C
   |
@@ -454,6 +462,7 b' Doing the actual push: hook abort'
   searching for changes
   transaction abort!
   rollback completed
+  changegroup hook: HG_BUNDLE2-EXP=1 HG_NEW_OBSMARKERS=0 HG_SOURCE=bundle2 HG_URL=bundle2
   abort: b2x-pretransactionclose.failpush hook exited with status 1
   [255]
 
@@ -463,6 +472,7 b' Doing the actual push: hook abort'
   abort: b2x-pretransactionclose.failpush hook exited with status 1
   remote: transaction abort!
   remote: rollback completed
+  remote: changegroup hook: HG_BUNDLE2-EXP=1 HG_NEW_OBSMARKERS=0 HG_SOURCE=bundle2 HG_URL=bundle2
   [255]
 
   $ hg -R main push http://localhost:$HGPORT2/ -r e7ec4e813ba6