tests/test-add.out

merge: allow smarter tool configuration

Add [merge-tool] hgrc section with:
 <tool>.executable = name or path (<tool>)
 <tool>.args = args with $local/base/other/output ($local $base $other)
 <tool>.priority = priority (default 0)
 <tool>.binary = handles binary (False)
 <tool>.symlink = handles symlinks (False)
 <tool>.checkconflict = check for conflict markers (False)
 <tool>.premerge = try internal simplemerge (True if not binary or symlink)

Four built-in tools: internal:{merge,local,other,fail}

Add [merge-patterns] section of the form:
 <pattern> = <tool>

Priority of settings is:
 HGMERGE
 merge-patterns
 ui:merge
 merge-tools by priority
 hgmerge, if it can be found

Changes:
 unsuccessful merges leave .orig files

adding a
? a
adding a
A a
A a
? b
A a
A b
% should fail
b already tracked!
A a
A b
% should fail
a already tracked!
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
merging a
warning: conflicts during merge.
merging a failed!
0 files updated, 0 files merged, 0 files removed, 1 files unresolved
There are unresolved merges, you can redo the full merge using:
  hg update -C 2
  hg merge 1
M a
? a.orig
% should fail
a already tracked!
M a
? a.orig
% issue683
R a
? a.orig
M a
? a.orig
c does not exist!
d does not exist!
M a
A c
? a.orig