rust-nodemap: accounting for dead blocks
By the very append-only nature of the `NodeTree`, inserting
new blocks has the effect of making some of the older ones
useless as they become unreachable.
Therefore some automatic housekeeping will need to be provided.
This is standard procedure in the word of databases, under names
such as "repack" or "vacuum".
The new `masked_readonly_blocks()` will provide callers with
useful information to decide if the nodetree is ripe for
repacking, but all the `NodeTree` can provide is how many
blocks have been masked in the currently mutable part. Analysing
the readonly part would be way too long to do it for each
transaction and defeat the whole purpose of nodemap persistence.
Serializing callers (from the Python layer) will get this figure
before each extraction and maintain an aggregate counter of
unreachable blocks separately.
Note: at this point, the most efficient repacking is just to restart
afresh with a full rescan.
Differential Revision: https://phab.mercurial-scm.org/D8097
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