procutil: make stream detection in make_line_buffered more correct and strict
In make_line_buffered(), we don’t want to wrap the stream if we know that lines
get flushed to the underlying raw stream already.
Previously, the heuristic was too optimistic. It assumed that any stream which
is not an instance of io.BufferedIOBase doesn’t need wrapping. However, there
are buffered streams that aren’t instances of io.BufferedIOBase, like
Mercurial’s own winstdout.
The new logic is different in two ways:
First, only for the check, if unwraps any combination of WriteAllWrapper and
winstdout.
Second, it skips wrapping the stream only if it is an instance of io.RawIOBase
(or already wrapped). If it is an instance of io.BufferedIOBase, it gets
wrapped. In any other case, the function raises an exception. This ensures
that, if an unknown stream is passed or we add another wrapper in the future,
we don’t wrap the stream if it’s already line buffered or not wrap the stream
if it’s not line buffered. In fact, this was already helpful during development
of this change. Without it, I possibly would have forgot that WriteAllWrapper
needs to be ignored for the check, leading to unnecessary wrapping if stdout is
unbuffered.
The alternative would have been to always wrap unknown streams. However, I
don’t think that anyone would benefit from being less strict. We can expect
streams from the standard library to be subclassing either io.RawIOBase or
io.BufferedIOBase, so running Mercurial in the standard way should not regress
by this change. Py2exe might replace sys.stdout and sys.stderr, but that
currently breaks Mercurial anyway and also these streams don’t claim to be
interactive, so this function is not called for them.
Testing recorded "modified" files for merge commit
==================================================
This file shows what hg says are "modified" files for a merge commit
(hg log -T {files}), somewhat exhaustively.
This file test multiple corner case.
For merges that involve files contents changing, check test-merge-combination-file-content.t
For merges that involve executable bit changing, check test-merge-combination-exec-bytes.t
Case with multiple or zero merge ancestors, copies/renames, and identical file contents
with different filelog revisions are not currently covered.
$ . $TESTDIR/testlib/merge-combination-util.sh
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