posix: always seek to EOF when opening a file in append mode
Python 3 already does this, so skip it there.
Consider the program:
#include <stdio.h>
int main() {
FILE *f = fopen("narf", "w");
fprintf(f, "narf\n");
fclose(f);
f = fopen("narf", "a");
printf("%ld\n", ftell(f));
fprintf(f, "troz\n");
printf("%ld\n", ftell(f));
return 0;
}
on macOS, FreeBSD, and Linux with glibc, this program prints
5
10
but on musl libc (Alpine Linux and probably others) this prints
0
10
By my reading of
https://pubs.opengroup.org/onlinepubs/009695399/functions/fopen.html
this is technically correct, specifically:
> Opening a file with append mode (a as the first character in the
> mode argument) shall cause all subsequent writes to the file to be
> forced to the then current end-of-file, regardless of intervening
> calls to fseek().
in other words, the file position doesn't really matter in append-mode
files, and we can't depend on it being at all meaningful unless we
perform a seek() before tell() after open(..., 'a'). Experimentally
after a .write() we can do a .tell() and it'll always be reasonable,
but I'm unclear from reading the specification if that's a smart thing
to rely on. This matches what we do on Windows and what Python 3 does
for free, so let's just be consistent. Thanks to Yuya for the idea.
$ cat >> $HGRCPATH <<EOF
> [experimental]
> bundle-phases=yes
> [extensions]
> strip=
> drawdag=$TESTDIR/drawdag.py
> EOF
Set up repo with linear history
$ hg init linear
$ cd linear
$ hg debugdrawdag <<'EOF'
> E
> |
> D
> |
> C
> |
> B
> |
> A
> EOF
$ hg phase --public A
$ hg phase --force --secret D
$ hg log -G -T '{desc} {phase}\n'
o E secret
|
o D secret
|
o C draft
|
o B draft
|
o A public
Phases are restored when unbundling
$ hg bundle --base B -r E bundle
3 changesets found
$ hg debugbundle bundle
Stream params: {Compression: BZ}
changegroup -- {nbchanges: 3, targetphase: 2, version: 02} (mandatory: True)
26805aba1e600a82e93661149f2313866a221a7b
f585351a92f85104bff7c284233c338b10eb1df7
9bc730a19041f9ec7cb33c626e811aa233efb18c
cache:rev-branch-cache -- {} (mandatory: False)
phase-heads -- {} (mandatory: True)
26805aba1e600a82e93661149f2313866a221a7b draft
$ hg strip --no-backup C
$ hg unbundle -q bundle
$ rm bundle
$ hg log -G -T '{desc} {phase}\n'
o E secret
|
o D secret
|
o C draft
|
o B draft
|
o A public
Root revision's phase is preserved
$ hg bundle -a bundle
5 changesets found
$ hg strip --no-backup A
$ hg unbundle -q bundle
$ rm bundle
$ hg log -G -T '{desc} {phase}\n'
o E secret
|
o D secret
|
o C draft
|
o B draft
|
o A public
Completely public history can be restored
$ hg phase --public E
$ hg bundle -a bundle
5 changesets found
$ hg strip --no-backup A
$ hg unbundle -q bundle
$ rm bundle
$ hg log -G -T '{desc} {phase}\n'
o E public
|
o D public
|
o C public
|
o B public
|
o A public
Direct transition from public to secret can be restored
$ hg phase --secret --force D
$ hg bundle -a bundle
5 changesets found
$ hg strip --no-backup A
$ hg unbundle -q bundle
$ rm bundle
$ hg log -G -T '{desc} {phase}\n'
o E secret
|
o D secret
|
o C public
|
o B public
|
o A public
Revisions within bundle preserve their phase even if parent changes its phase
$ hg phase --draft --force B
$ hg bundle --base B -r E bundle
3 changesets found
$ hg strip --no-backup C
$ hg phase --public B
$ hg unbundle -q bundle
$ rm bundle
$ hg log -G -T '{desc} {phase}\n'
o E secret
|
o D secret
|
o C draft
|
o B public
|
o A public
Phase of ancestors of stripped node get advanced to accommodate child
$ hg bundle --base B -r E bundle
3 changesets found
$ hg strip --no-backup C
$ hg phase --force --secret B
$ hg unbundle -q bundle
$ rm bundle
$ hg log -G -T '{desc} {phase}\n'
o E secret
|
o D secret
|
o C draft
|
o B draft
|
o A public
Unbundling advances phases of changesets even if they were already in the repo.
To test that, create a bundle of everything in draft phase and then unbundle
to see that secret becomes draft, but public remains public.
$ hg phase --draft --force A
$ hg phase --draft E
$ hg bundle -a bundle
5 changesets found
$ hg phase --public A
$ hg phase --secret --force E
$ hg unbundle -q bundle
$ rm bundle
$ hg log -G -T '{desc} {phase}\n'
o E draft
|
o D draft
|
o C draft
|
o B draft
|
o A public
Unbundling change in the middle of a stack does not affect later changes
$ hg strip --no-backup E
$ hg phase --secret --force D
$ hg log -G -T '{desc} {phase}\n'
o D secret
|
o C draft
|
o B draft
|
o A public
$ hg bundle --base A -r B bundle
1 changesets found
$ hg unbundle -q bundle
$ rm bundle
$ hg log -G -T '{desc} {phase}\n'
o D secret
|
o C draft
|
o B draft
|
o A public
$ cd ..
Set up repo with non-linear history
$ hg init non-linear
$ cd non-linear
$ hg debugdrawdag <<'EOF'
> D E
> |\|
> B C
> |/
> A
> EOF
$ hg phase --public C
$ hg phase --force --secret B
$ hg log -G -T '{node|short} {desc} {phase}\n'
o 03ca77807e91 E draft
|
| o 4e4f9194f9f1 D secret
|/|
o | dc0947a82db8 C public
| |
| o 112478962961 B secret
|/
o 426bada5c675 A public
Restore bundle of entire repo
$ hg bundle -a bundle
5 changesets found
$ hg debugbundle bundle
Stream params: {Compression: BZ}
changegroup -- {nbchanges: 5, targetphase: 2, version: 02} (mandatory: True)
426bada5c67598ca65036d57d9e4b64b0c1ce7a0
112478962961147124edd43549aedd1a335e44bf
dc0947a82db884575bb76ea10ac97b08536bfa03
4e4f9194f9f181c57f62e823e8bdfa46ab9e4ff4
03ca77807e919db8807c3749086dc36fb478cac0
cache:rev-branch-cache -- {} (mandatory: False)
phase-heads -- {} (mandatory: True)
dc0947a82db884575bb76ea10ac97b08536bfa03 public
03ca77807e919db8807c3749086dc36fb478cac0 draft
$ hg strip --no-backup A
$ hg unbundle -q bundle
$ rm bundle
$ hg log -G -T '{node|short} {desc} {phase}\n'
o 03ca77807e91 E draft
|
| o 4e4f9194f9f1 D secret
|/|
o | dc0947a82db8 C public
| |
| o 112478962961 B secret
|/
o 426bada5c675 A public
$ hg bundle --base 'A + C' -r D bundle
2 changesets found
$ hg debugbundle bundle
Stream params: {Compression: BZ}
changegroup -- {nbchanges: 2, targetphase: 2, version: 02} (mandatory: True)
112478962961147124edd43549aedd1a335e44bf
4e4f9194f9f181c57f62e823e8bdfa46ab9e4ff4
cache:rev-branch-cache -- {} (mandatory: False)
phase-heads -- {} (mandatory: True)
$ rm bundle
$ hg bundle --base A -r D bundle
3 changesets found
$ hg debugbundle bundle
Stream params: {Compression: BZ}
changegroup -- {nbchanges: 3, targetphase: 2, version: 02} (mandatory: True)
112478962961147124edd43549aedd1a335e44bf
dc0947a82db884575bb76ea10ac97b08536bfa03
4e4f9194f9f181c57f62e823e8bdfa46ab9e4ff4
cache:rev-branch-cache -- {} (mandatory: False)
phase-heads -- {} (mandatory: True)
dc0947a82db884575bb76ea10ac97b08536bfa03 public
$ rm bundle
$ hg bundle --base 'B + C' -r 'D + E' bundle
2 changesets found
$ hg debugbundle bundle
Stream params: {Compression: BZ}
changegroup -- {nbchanges: 2, targetphase: 2, version: 02} (mandatory: True)
4e4f9194f9f181c57f62e823e8bdfa46ab9e4ff4
03ca77807e919db8807c3749086dc36fb478cac0
cache:rev-branch-cache -- {} (mandatory: False)
phase-heads -- {} (mandatory: True)
03ca77807e919db8807c3749086dc36fb478cac0 draft
$ rm bundle