$ cat >> $HGRCPATH << EOF

  > [extensions]

  > fastannotate=

  > [fastannotate]

  > mainbranch=main

  > EOF

  $ hg init repo

  $ cd repo

add or rename files on top of the master branch

  $ echo a1 > a

  $ echo b1 > b

  $ hg commit -qAm 1

  $ hg bookmark -i main

  $ hg fastannotate --debug -nf b

  fastannotate: b: 1 new changesets in the main branch

  0 b: b1

  $ hg fastannotate --debug -nf a

  fastannotate: a: 1 new changesets in the main branch

  0 a: a1

  $ echo a2 >> a

  $ cat > b << EOF

  > b0

  > b1

  > EOF

  $ hg mv a t

  $ hg mv b a

  $ hg mv t b

  $ hg commit -m 'swap names'

existing linelogs are not helpful with such renames in side branches

  $ hg fastannotate --debug -nf a

  fastannotate: a: linelog cannot help in annotating this revision

  1 a: b0

  0 b: b1

  $ hg fastannotate --debug -nf b

  fastannotate: b: linelog cannot help in annotating this revision

  0 a: a1

  1 b: a2

move main branch forward, rebuild should happen

  $ hg bookmark -i main -r . -q

  $ hg fastannotate --debug -nf b

  fastannotate: b: cache broken and deleted

  fastannotate: b: 2 new changesets in the main branch

  0 a: a1

  1 b: a2

  $ hg fastannotate --debug -nf b

  fastannotate: b: using fast path (resolved fctx: True)

  0 a: a1

  1 b: a2

for rev 0, the existing linelog is still useful for a, but not for b

  $ hg fastannotate --debug -nf a -r 0

  fastannotate: a: using fast path (resolved fctx: True)

  0 a: a1

  $ hg fastannotate --debug -nf b -r 0

  fastannotate: b: linelog cannot help in annotating this revision

  0 b: b1

a rebuild can also be triggered if "the main branch last time" mismatches

  $ echo a3 >> a

  $ hg commit -m a3

  $ cat >> b << EOF

  > b3

  > b4

  > EOF

  $ hg commit -m b4

  $ hg bookmark -i main -q

  $ hg fastannotate --debug -nf a

  fastannotate: a: cache broken and deleted

  fastannotate: a: 3 new changesets in the main branch

  1 a: b0

  0 b: b1

  2 a: a3

  $ hg fastannotate --debug -nf a

  fastannotate: a: using fast path (resolved fctx: True)

  1 a: b0

  0 b: b1

  2 a: a3

linelog can be updated without being helpful

  $ hg mv a t

  $ hg mv b a

  $ hg mv t b

  $ hg commit -m 'swap names again'

  $ hg fastannotate --debug -nf b

  fastannotate: b: 1 new changesets in the main branch

  1 a: b0

  0 b: b1

  2 a: a3

  $ hg fastannotate --debug -nf b

  fastannotate: b: linelog cannot help in annotating this revision

  1 a: b0

  0 b: b1

  2 a: a3

move main branch forward again, rebuilds are one-time

  $ hg bookmark -i main -q

  $ hg fastannotate --debug -nf a

  fastannotate: a: cache broken and deleted

  fastannotate: a: 4 new changesets in the main branch

  0 a: a1

  1 b: a2

  3 b: b3

  3 b: b4

  $ hg fastannotate --debug -nf b

  fastannotate: b: cache broken and deleted

  fastannotate: b: 4 new changesets in the main branch

  1 a: b0

  0 b: b1

  2 a: a3

  $ hg fastannotate --debug -nf a

  fastannotate: a: using fast path (resolved fctx: True)

  0 a: a1

  1 b: a2

  3 b: b3

  3 b: b4

  $ hg fastannotate --debug -nf b

  fastannotate: b: using fast path (resolved fctx: True)

  1 a: b0

  0 b: b1

  2 a: a3

list changeset hashes to improve readability

  $ hg log -T '{rev}:{node}\n'

  4:980e1ab8c516350172928fba95b49ede3b643dca

  3:14e123fedad9f491f5dde0beca2a767625a0a93a

  2:96495c41e4c12218766f78cdf244e768d7718b0f

  1:35c2b781234c994896aba36bd3245d3104e023df

  0:653e95416ebb5dbcc25bbc7f75568c9e01f7bd2f

annotate a revision not in the linelog. linelog cannot be used, but does not get rebuilt either

  $ hg fastannotate --debug -nf a -r 96495c41e4c12218766f78cdf244e768d7718b0f

  fastannotate: a: linelog cannot help in annotating this revision

  1 a: b0

  0 b: b1

  2 a: a3

  $ hg fastannotate --debug -nf a -r 2

  fastannotate: a: linelog cannot help in annotating this revision

  1 a: b0

  0 b: b1

  2 a: a3

  $ hg fastannotate --debug -nf a -r .

  fastannotate: a: using fast path (resolved fctx: True)

  0 a: a1

  1 b: a2

  3 b: b3

  3 b: b4

annotate an ancient revision where the path matches. linelog can be used

  $ hg fastannotate --debug -nf a -r 0

  fastannotate: a: using fast path (resolved fctx: True)

  0 a: a1

  $ hg fastannotate --debug -nf a -r 653e95416ebb5dbcc25bbc7f75568c9e01f7bd2f

  fastannotate: a: using fast path (resolved fctx: False)

  0 a: a1