contrib/hgclient.py

log: rewrite default template to use labels (issue2866)

This is a complete rewrite of the default template to use labels. This
seems ultimately useless to me in most cases. The biggest benefit of
this patch to me seems to be a fairly complicated example of the
templating engine. It was a lot of hard work to figure out the precise
acceptable syntax, since it's almost undocumented. Hat tip to Steve
Losh's smartlog template, which helped me figure out a lot of the
syntax. Hopefully later I can use the present default log template
as an example for documenting the templating engine.

A test is attached. My goal was to match the --color=debug output,
which may differ slightly in newlines from the actual ANSI escape
codes output. I consider this an acceptable invisible deviation.

There seems to be a considerable slowdown with this rewrite.

Before:

    $ time hg log -T default -r .~100::. > /dev/null
    real  0m0.882s
    user  0m0.812s
    sys   0m0.064s
    $ time hg log -T default -r .~100::. > /dev/null
    real  0m0.872s
    user  0m0.796s
    sys   0m0.068s
    $ time hg log -T default -r .~100::. > /dev/null
    real  0m0.917s
    user  0m0.836s
    sys   0m0.076s

After:

    $ time hg log -T default -r .~100::. > /dev/null
    real  0m1.480s
    user  0m1.392s
    sys   0m0.072s
    $ time hg log -T default -r .~100::. > /dev/null
    real  0m1.500s
    user  0m1.400s
    sys   0m0.088s
    $ time hg log -T default -r .~100::. > /dev/null
    real  0m1.462s
    user  0m1.364s
    sys   0m0.092s

Following the maxim, "make it work, profile, make it faster, in that
order", I deem this slowdown acceptable for now.

I suspect but have not confirmed that a big slowdown comes from
calling keywords twice in the file templates, once to test the
existence of output and again to actually list the output. If so, a
simple speedup might be to improve the templating engine to cache
keywords when called more than once on the same revision.

TODO: I found a bug while working on this. The following stack traces:

    hg log -r . -T '{ifcontains(phase, "secret public", "lol", "omg")}\n'

# A minimal client for Mercurial's command server

import sys, struct, subprocess, cStringIO

def connect(path=None):
    cmdline = ['hg', 'serve', '--cmdserver', 'pipe']
    if path:
        cmdline += ['-R', path]

    server = subprocess.Popen(cmdline, stdin=subprocess.PIPE,
                              stdout=subprocess.PIPE)

    return server

def writeblock(server, data):
    server.stdin.write(struct.pack('>I', len(data)))
    server.stdin.write(data)
    server.stdin.flush()

def readchannel(server):
    data = server.stdout.read(5)
    if not data:
        raise EOFError
    channel, length = struct.unpack('>cI', data)
    if channel in 'IL':
        return channel, length
    else:
        return channel, server.stdout.read(length)

def sep(text):
    return text.replace('\\', '/')

def runcommand(server, args, output=sys.stdout, error=sys.stderr, input=None,
               outfilter=lambda x: x):
    print '*** runcommand', ' '.join(args)
    sys.stdout.flush()
    server.stdin.write('runcommand\n')
    writeblock(server, '\0'.join(args))

    if not input:
        input = cStringIO.StringIO()

    while True:
        ch, data = readchannel(server)
        if ch == 'o':
            output.write(outfilter(data))
            output.flush()
        elif ch == 'e':
            error.write(data)
            error.flush()
        elif ch == 'I':
            writeblock(server, input.read(data))
        elif ch == 'L':
            writeblock(server, input.readline(data))
        elif ch == 'r':
            ret, = struct.unpack('>i', data)
            if ret != 0:
                print ' [%d]' % ret
            return ret
        else:
            print "unexpected channel %c: %r" % (ch, data)
            if ch.isupper():
                return

def check(func, repopath=None):
    sys.stdout.flush()
    server = connect(repopath)
    try:
        return func(server)
    finally:
        server.stdin.close()
        server.wait()