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
> [extensions]
> show =
> EOF
$ hg init repo0
$ cd repo0
Empty repo / no checkout results in error
$ hg show stack
abort: stack view only available when there is a working directory
[255]
Stack displays single draft changeset as root revision
$ echo 0 > foo
$ hg -q commit -A -m 'commit 0'
$ hg show stack
@ 9f17 commit 0
Stack displays multiple draft changesets
$ echo 1 > foo
$ hg commit -m 'commit 1'
$ echo 2 > foo
$ hg commit -m 'commit 2'
$ echo 3 > foo
$ hg commit -m 'commit 3'
$ echo 4 > foo
$ hg commit -m 'commit 4'
$ hg show stack
@ 2737 commit 4
o d1a6 commit 3
o 128c commit 2
o 181c commit 1
o 9f17 commit 0
Public parent of draft base is displayed, separated from stack
$ hg phase --public -r 0
$ hg show stack
@ 2737 commit 4
o d1a6 commit 3
o 128c commit 2
o 181c commit 1
/ (stack base)
o 9f17 commit 0
$ hg phase --public -r 1
$ hg show stack
@ 2737 commit 4
o d1a6 commit 3
o 128c commit 2
/ (stack base)
o 181c commit 1
Draft descendants are shown
$ hg -q up 2
$ hg show stack
o 2737 commit 4
o d1a6 commit 3
@ 128c commit 2
/ (stack base)
o 181c commit 1
$ hg -q up 3
$ hg show stack
o 2737 commit 4
@ d1a6 commit 3
o 128c commit 2
/ (stack base)
o 181c commit 1
working dir on public changeset should display special message
$ hg -q up 1
$ hg show stack
(empty stack; working directory parent is a published changeset)
Branch point in descendants displayed at top of graph
$ hg -q up 3
$ echo b > foo
$ hg commit -m 'commit 5 (new dag branch)'
created new head
$ hg -q up 2
$ hg show stack
\ / (multiple children)
|
o d1a6 commit 3
@ 128c commit 2
/ (stack base)
o 181c commit 1
$ cd ..
Base is stopped at merges
$ hg init merge-base
$ cd merge-base
$ echo 0 > foo
$ hg -q commit -A -m initial
$ echo h1 > foo
$ hg commit -m 'head 1'
$ hg -q up 0
$ echo h2 > foo
$ hg -q commit -m 'head 2'
$ hg phase --public -r 0:tip
$ hg -q up 1
$ hg merge -t :local 2
0 files updated, 1 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg commit -m 'merge heads'
TODO doesn't yet handle case where wdir is a draft merge
$ hg show stack
@ 8ee9 merge heads
/ (stack base)
o 5947 head 1
$ echo d1 > foo
$ hg commit -m 'draft 1'
$ echo d2 > foo
$ hg commit -m 'draft 2'
$ hg show stack
@ 430d draft 2
o 787b draft 1
/ (stack base)
o 8ee9 merge heads
$ cd ..
Now move on to stacks when there are more commits after the base branchpoint
$ hg init public-rebase
$ cd public-rebase
$ echo 0 > foo
$ hg -q commit -A -m 'base'
$ hg phase --public -r .
$ echo d1 > foo
$ hg commit -m 'draft 1'
$ echo d2 > foo
$ hg commit -m 'draft 2'
$ hg -q up 0
$ echo 1 > foo
$ hg commit -m 'new 1'
created new head
$ echo 2 > foo
$ hg commit -m 'new 2'
$ hg -q up 2
Newer draft heads don't impact output
$ hg show stack
@ eaff draft 2
o 2b21 draft 1
/ (stack base)
o b66b base
Newer public heads are rendered
$ hg phase --public -r '::tip'
$ hg show stack
o baa4 new 2
/ (2 commits ahead)
:
: (stack head)
: @ eaff draft 2
: o 2b21 draft 1
:/ (stack base)
o b66b base
If rebase is available, we show a hint how to rebase to that head
$ hg --config extensions.rebase= show stack
o baa4 new 2
/ (2 commits ahead; hg rebase --source 2b21 --dest baa4)
:
: (stack head)
: @ eaff draft 2
: o 2b21 draft 1
:/ (stack base)
o b66b base
Similar tests but for multiple heads
$ hg -q up 0
$ echo h2 > foo
$ hg -q commit -m 'new head 2'
$ hg phase --public -r .
$ hg -q up 2
$ hg show stack
o baa4 new 2
/ (2 commits ahead)
: o 9a84 new head 2
:/ (1 commits ahead)
:
: (stack head)
: @ eaff draft 2
: o 2b21 draft 1
:/ (stack base)
o b66b base
$ hg --config extensions.rebase= show stack
o baa4 new 2
/ (2 commits ahead; hg rebase --source 2b21 --dest baa4)
: o 9a84 new head 2
:/ (1 commits ahead; hg rebase --source 2b21 --dest 9a84)
:
: (stack head)
: @ eaff draft 2
: o 2b21 draft 1
:/ (stack base)
o b66b base