tests/test-fastannotate-renames.t

dirstate: when calling rebuild(), avoid some N^2 codepaths

I had a user repo with 200k files in it. Calling `hg debugrebuilddirstate` took
tens of minutes (I didn't wait for it). In that situation,
changedfiles==allfiles, and both are lists. This meant that we had to run an
average of 100k comparisons, for each of 200k files, just to check whether a
file needed to have normallookup called (it always did), or drop.

While it's probably not a huge issue, in my very awkward synthetic benchmark I
wrote (not using a benchmark library or anything), I was seeing some slowdowns
for small-changedfiles and very-large-allfiles invocations, with an inflection
somewhere around 10 items in changedfiles (regardless of the size of allfiles);
above 10 items in changedfiles, the new code appears to always be faster. For
the case of 50k files in changedfiles and the same items in allfiles, I'm seeing
differences of 15s of just running comparisons vs. 0.003793s. I haven't bothered
to run a comparison of 200k items in changedfiles and allfiles. :)

Differential Revision: https://phab.mercurial-scm.org/D7665

  $ 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