tests/test-merge-combination.t

rust-performance: introduce FastHashMap type alias for HashMap

Rust's default hashing is slow, because it is meant for preventing collision
attacks.
For all of the current Rust code, we don't care about those attacks, because
if an person with bad intentions has write access to your repo, you have other
issues.

I've chosen to use the TwoXHash crate because it was made by a reputable member
of the Rust community and has very good benchmarks.

For now it does not seem to improve performance by much for the current code,
but it's something else to not worry about when benchmarking code: in a
previous experiment with copytracing in Rust, it accounted for more than 10%
of the time of the entire script.

Differential Revision: https://phab.mercurial-scm.org/D7116

This file shows what hg says are "modified" files for a merge commit
(hg log -T {files}), somewhat exhaustively.
It shows merges that involves files contents changing, and merges that
involve executable bit changing, but not merges with multiple or zero
merge ancestors, nor copies/renames, and nor identical file contents
with different filelog revisions.

genmerges is the workhorse. Given:
- a range function describing the possible values for file a
- a isgood function to filter out uninteresting combination
- a createfile function to actually write the values for file a on the
filesystem
it print a series of lines that look like: abcd C: output of -T {files}
describing the file a at respectively the base, p2, p1, merge
revision. "C" indicates that hg merge had conflicts.
  $ genmerges () {
  >   for base in `range` -; do
  >     for r1 in `range $base` -; do
  >       for r2 in `range $base $r1` -; do
  >         for m in `range $base $r1 $r2` -; do
  >           line="$base$r1$r2$m"
  >           isgood $line || continue
  >           hg init repo
  >           cd repo
  >           make_commit () {
  >             v=$1; msg=$2; file=$3;
  >             if [ $v != - ]; then
  >               createfile $v
  >             else
  >               if [ -f a ]
  >               then rm a
  >               else touch $file
  >               fi
  >             fi
  >             hg commit -q -Am $msg || exit 123
  >           }
  >           echo foo > foo
  >           make_commit $base base b
  >           make_commit $r1 r1 c
  >           hg up -r 0 -q
  >           make_commit $r2 r2 d
  >           hg merge -q -r 1 > ../output 2>&1
  >           if [ $? -ne 0 ]; then rm -f *.orig; hg resolve -m --all -q; fi
  >           if [ -s ../output ]; then conflicts=" C"; else conflicts="  "; fi
  >           make_commit $m m e
  >           if [ $m = $r1 ] && [ $m = $r2 ]
  >           then expected=
  >           elif [ $m = $r1 ]
  >           then if [ $base = $r2 ]
  >                then expected=
  >                else expected=a
  >                fi
  >           elif [ $m = $r2 ]
  >           then if [ $base = $r1 ]
  >                then expected=
  >                else expected=a
  >                fi
  >           else expected=a
  >           fi
  >           got=`hg log -r 3 --template '{files}\n' | tr -d 'e '`
  >           if [ "$got" = "$expected" ]
  >           then echo "$line$conflicts: agree on \"$got\""
  >           else echo "$line$conflicts: hg said \"$got\", expected \"$expected\""
  >           fi
  >           cd ../
  >           rm -rf repo
  >         done
  >       done
  >     done
  >   done
  > }

All the merges of various file contents.

  $ range () {
  >   max=0
  >   for i in $@; do
  >     if [ $i = - ]; then continue; fi
  >     if [ $i -gt $max ]; then max=$i; fi
  >   done
  >   $TESTDIR/seq.py `expr $max + 1`
  > }
  $ isgood () { true; }
  $ createfile () {
  >   if [ -f a ] && [ "`cat a`" = $1 ]
  >   then touch $file
  >   else echo $v > a
  >   fi
  > }

  $ genmerges
  1111  : agree on ""
  1112  : agree on "a"
  111-  : agree on "a"
  1121  : agree on "a"
  1122  : agree on ""
  1123  : agree on "a"
  112-  : agree on "a"
  11-1  : hg said "", expected "a"
  11-2  : agree on "a"
  11--  : agree on ""
  1211  : agree on "a"
  1212  : agree on ""
  1213  : agree on "a"
  121-  : agree on "a"
  1221  : agree on "a"
  1222  : agree on ""
  1223  : agree on "a"
  122-  : agree on "a"
  1231 C: agree on "a"
  1232 C: agree on "a"
  1233 C: agree on "a"
  1234 C: agree on "a"
  123- C: agree on "a"
  12-1 C: agree on "a"
  12-2 C: hg said "", expected "a"
  12-3 C: agree on "a"
  12-- C: agree on "a"
  1-11  : hg said "", expected "a"
  1-12  : agree on "a"
  1-1-  : agree on ""
  1-21 C: agree on "a"
  1-22 C: hg said "", expected "a"
  1-23 C: agree on "a"
  1-2- C: agree on "a"
  1--1  : agree on "a"
  1--2  : agree on "a"
  1---  : agree on ""
  -111  : agree on ""
  -112  : agree on "a"
  -11-  : agree on "a"
  -121 C: agree on "a"
  -122 C: agree on "a"
  -123 C: agree on "a"
  -12- C: agree on "a"
  -1-1  : agree on ""
  -1-2  : agree on "a"
  -1--  : agree on "a"
  --11  : agree on ""
  --12  : agree on "a"
  --1-  : agree on "a"
  ---1  : agree on "a"
  ----  : agree on ""

All the merges of executable bit.

  $ range () {
  >   max=a
  >   for i in $@; do
  >     if [ $i = - ]; then continue; fi
  >     if [ $i > $max ]; then max=$i; fi
  >   done
  >   if [ $max = a ]; then echo f; else echo f x; fi
  > }
  $ isgood () { case $line in *f*x*) true;; *) false;; esac; }
  $ createfile () {
  >   if [ -f a ] && (([ -x a ] && [ $v = x ]) || (! [ -x a ] && [ $v != x ]))
  >   then touch $file
  >   else touch a; if [ $v = x ]; then chmod +x a; else chmod -x a; fi
  >   fi
  > }

#if execbit
  $ genmerges
  fffx  : agree on "a"
  ffxf  : agree on "a"
  ffxx  : agree on ""
  ffx-  : agree on "a"
  ff-x  : hg said "", expected "a"
  fxff  : hg said "", expected "a"
  fxfx  : hg said "a", expected ""
  fxf-  : agree on "a"
  fxxf  : agree on "a"
  fxxx  : agree on ""
  fxx-  : agree on "a"
  fx-f  : hg said "", expected "a"
  fx-x  : hg said "", expected "a"
  fx--  : hg said "", expected "a"
  f-fx  : agree on "a"
  f-xf  : agree on "a"
  f-xx  : hg said "", expected "a"
  f-x-  : agree on "a"
  f--x  : agree on "a"
  -ffx  : agree on "a"
  -fxf C: agree on "a"
  -fxx C: hg said "", expected "a"
  -fx- C: agree on "a"
  -f-x  : hg said "", expected "a"
  --fx  : agree on "a"
#endif

Files modified or cleanly merged, with no greatest common ancestors:

  $ hg init repo; cd repo
  $ touch a0 b0; hg commit -qAm 0
  $ hg up -qr null; touch a1 b1; hg commit -qAm 1
  $ hg merge -qr 0; rm b*; hg commit -qAm 2
  $ hg log -r . -T '{files}\n'
  b0 b1
  $ cd ../
  $ rm -rf repo

A few cases of criss-cross merges involving deletions (listing all
such merges is probably too much). Both gcas contain $files, so we
expect the final merge to behave like a merge with a single gca
containing $files.

  $ hg init repo; cd repo
  $ files="c1 u1 c2 u2"
  $ touch $files; hg commit -qAm '0 root'
  $ for f in $files; do echo f > $f; done; hg commit -qAm '1 gca1'
  $ hg up -qr0; hg revert -qr 1 --all; hg commit -qAm '2 gca2'
  $ hg up -qr 1; hg merge -qr 2; rm *1; hg commit -qAm '3 p1'
  $ hg up -qr 2; hg merge -qr 1; rm *2; hg commit -qAm '4 p2'
  $ hg merge -qr 3; echo f > u1; echo f > u2; rm -f c1 c2
  $ hg commit -qAm '5 merge with two gcas'
  $ hg log -r . -T '{files}\n' # expecting u1 u2
  
  $ cd ../
  $ rm -rf repo