tests/test-pull-http.t

filemerge: add support for partial conflict resolution by external tool

A common class of merge conflicts is in imports/#includes/etc. It's
relatively easy to write a tool that can resolve these conflicts,
perhaps by naively just unioning the statements and leaving any
cleanup to other tools to do later [1]. Such specialized tools cannot
generally resolve all conflicts in a file, of course. Let's therefore
call them "partial merge tools". Note that the internal simplemerge
algorithm is such a partial merge tool - one that only resolves
trivial "conflicts" where one side is unchanged or both sides change
in the same way.

One can also imagine having smarter language-aware partial tools that
merge the AST. It may be useful for such tools to interactively let
the user resolve any conflicts it can't resolve itself. However,
having the option of implementing it as a partial merge tool means
that the developer doesn't *need* to create a UI for it. Instead, the
user can resolve any remaining conflicts with their regular merge tool
(e.g. `:merge3` or `meld).

We don't currently have a way to let the user define such partial
merge tools. That's what this patch addresses. It lets the user
configure partial merge tools to run. Each tool can be configured to
run only on files matching certain patterns (e.g. "*.py"). The tool
takes three inputs (local, base, other) and resolves conflicts by
updating these in place. For example, let's say the inputs are these:


base:
```
import sys

def main():
  print('Hello')
```

local:
```
import os
import sys

def main():
  print('Hi')
```

other:
```
import re
import sys

def main():
  print('Howdy')
```

A partial merge tool could now resolve the conflicting imports by
replacing the import statements in *all* files by the following
snippet, while leaving the remainder of the files unchanged.

```
import os
import re
import sys
```

As a result, simplemerge and any regular merge tool that runs after
the partial merge tool(s) will consider the imports to be
non-conflicting and will only present the conflict in `main()` to the
user.

Differential Revision: https://phab.mercurial-scm.org/D12356

#if no-windows
For debugging: this is a pretty simple test that is a good candidate
for tracking down network-related bugs. Sometimes a command in this
hangs, so having showstack pre-loaded is sometimes helpful. This also
gives us a test that at least proves showstack can be loaded.
  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > showstack = $TESTDIR/../contrib/showstack.py
  > EOF
#endif

  $ hg init test
  $ cd test
  $ echo a > a
  $ hg ci -Ama
  adding a
  $ cd ..
  $ hg clone test test2
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd test2
  $ echo a >> a
  $ hg ci -mb

Cloning with a password in the URL should not save the password in .hg/hgrc:

  $ hg serve -p $HGPORT -d --pid-file=hg.pid -E errors.log
  $ cat hg.pid >> $DAEMON_PIDS
  $ hg clone http://foo:xyzzy@localhost:$HGPORT/ test3
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 2 changes to 1 files
  new changesets cb9a9f314b8b:ba677d0156c1
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cat test3/.hg/hgrc
  # example repository config (see 'hg help config' for more info)
  [paths]
  default = http://foo@localhost:$HGPORT/
  
  # path aliases to other clones of this repo in URLs or filesystem paths
  # (see 'hg help config.paths' for more info)
  #
  # default:pushurl = ssh://[e-mail]/hg/jdoes-fork
  # my-fork         = ssh://[e-mail]/hg/jdoes-fork
  # my-clone        = /home/jdoe/jdoes-clone
  
  [ui]
  # name and email (local to this repository, optional), e.g.
  # username = Jane Doe <[e-mail]>
  $ killdaemons.py

expect error, cloning not allowed

  $ echo '[web]' > .hg/hgrc
  $ echo 'allowpull = false' >> .hg/hgrc
  $ hg serve -p $HGPORT -d --pid-file=hg.pid -E errors.log
  $ cat hg.pid >> $DAEMON_PIDS
  $ hg clone http://localhost:$HGPORT/ test4 # bundle2+
  abort: authorization failed
  [255]
  $ hg clone http://localhost:$HGPORT/ test4 --config devel.legacy.exchange=bundle1
  abort: authorization failed
  [255]
  $ killdaemons.py

serve errors

  $ cat errors.log
  $ req() {
  >     hg serve -p $HGPORT -d --pid-file=hg.pid -E errors.log
  >     cat hg.pid >> $DAEMON_PIDS
  >     hg --cwd ../test pull http://localhost:$HGPORT/
  >     killdaemons.py hg.pid
  >     echo % serve errors
  >     cat errors.log
  > }

expect error, pulling not allowed

  $ req
  pulling from http://localhost:$HGPORT/
  abort: authorization failed
  % serve errors

  $ cd ..