Enable obsolete markers

  $ cat >> $HGRCPATH << EOF

  > [experimental]

  > evolution=createmarkers

  > [phases]

  > publish=False

  > EOF

Build a repo with some cacheable bits:

  $ hg init a

  $ cd a

  $ echo a > a

  $ hg ci -qAm0

  $ hg tag t1

  $ hg book -i bk1

  $ hg branch -q b2

  $ hg ci -Am1

  $ hg tag t2

  $ echo dumb > dumb

  $ hg ci -qAmdumb

  $ hg debugobsolete b1174d11b69e63cb0c5726621a43c859f0858d7f

  $ hg phase -pr t1

  $ hg phase -fsr t2

Make a helper function to check cache damage invariants:

- command output shouldn't change

- cache should be present after first use

- corruption/repair should be silent (no exceptions or warnings)

- cache should survive deletion, overwrite, and append

- unreadable / unwriteable caches should be ignored

- cache should be rebuilt after corruption

  $ damage() {

  >  CMD=$1

  >  CACHE=.hg/cache/$2

  >  CLEAN=$3

  >  hg $CMD > before

  >  test -f $CACHE || echo "not present"

  >  echo bad > $CACHE

  >  test -z "$CLEAN" || $CLEAN

  >  hg $CMD > after

  >  diff -u before after || echo "*** overwrite corruption"

  >  echo corruption >> $CACHE

  >  test -z "$CLEAN" || $CLEAN

  >  hg $CMD > after

  >  diff -u before after || echo "*** append corruption"

  >  rm $CACHE

  >  mkdir $CACHE

  >  test -z "$CLEAN" || $CLEAN

  >  hg $CMD > after

  >  diff -u before after || echo "*** read-only corruption"

  >  test -d $CACHE || echo "*** directory clobbered"

  >  rmdir $CACHE

  >  test -z "$CLEAN" || $CLEAN

  >  hg $CMD > after

  >  diff -u before after || echo "*** missing corruption"

  >  test -f $CACHE || echo "not rebuilt"

  > }

Beat up tags caches:

  $ damage "tags --hidden" tags2

  $ damage tags tags2-visible

  $ damage "tag -f t3" hgtagsfnodes1

Beat up hidden cache:

  $ damage log hidden

Beat up branch caches:

  $ damage branches branch2-base "rm .hg/cache/branch2-[vs]*"

  $ damage branches branch2-served "rm .hg/cache/branch2-[bv]*"

  $ damage branches branch2-visible

  $ damage "log -r branch(.)" rbc-names-v1

  $ damage "log -r branch(default)" rbc-names-v1

  $ damage "log -r branch(b2)" rbc-revs-v1

We currently can't detect an rbc cache with unknown names:

  $ damage "log -qr branch(b2)" rbc-names-v1

  --- before	* (glob)

  +++ after	* (glob)

  @@ -1,8 +?,0 @@ (glob)

  -2:5fb7d38b9dc4

  -3:60b597ffdafa

  -4:b1174d11b69e

  -5:6354685872c0

  -6:5ebc725f1bef

  -7:7b76eec2f273

  -8:ef3428d9d644

  -9:ba7a936bc03c

  *** append corruption