--- a/mercurial/filemerge.py	Sun Feb 03 19:29:05 2008 -0600
+++ b/mercurial/filemerge.py	Sun Feb 03 19:29:05 2008 -0600
@@ -7,7 +7,57 @@
 
 from node import *
 from i18n import _
-import util, os, tempfile, context
+import util, os, tempfile, context, simplemerge, re
+
+def _toolstr(ui, tool, part, default=None):
+    return ui.config("merge-tools", tool + "." + part, default)
+
+def _toolbool(ui, tool, part, default=False):
+    return ui.configbool("merge-tools", tool + "." + part, default)
+
+def _findtool(ui, tool):
+    return util.find_exe(_toolstr(ui, tool, "executable", tool))
+
+def _picktool(repo, ui, path, binary, symlink):
+    def check(tool, pat, symlink, binary):
+        tmsg = tool
+        if pat:
+            tmsg += " specified for " + pat
+        if pat and not _findtool(ui, tool): # skip search if not matching
+            ui.warn(_("couldn't find merge tool %s\n") % tmsg)
+        elif symlink and not _toolbool(ui, tool, "symlink"):
+            ui.warn(_("tool %s can't handle symlinks\n") % tmsg)
+        elif binary and not _toolbool(ui, tool, "binary"):
+            ui.warn(_("tool %s can't handle binary\n") % tmsg)
+        else:
+            return True
+        return False
+
+    # HGMERGE takes precedence
+    if os.environ.get("HGMERGE"):
+        return os.environ.get("HGMERGE")
+
+    # then patterns
+    for pattern, tool in ui.configitems("merge-patterns"):
+        mf = util.matcher(repo.root, "", [pat], [], [])[1]
+        if mf(path) and check(tool, pat, symlink, False):
+                return tool
+
+    # then merge tools
+    tools = {}
+    for k,v in ui.configitems("merge-tools"):
+        t = k.split('.')[0]
+        if t not in tools:
+            tools[t] = int(_toolstr(ui, t, "priority", "0"))
+    tools = [(-p,t) for t,p in tools.items()]
+    tools.sort()
+    if ui.config("ui", "merge"):
+        tools.insert(0, (None, ui.config("ui", "merge"))) # highest priority
+    tools.append((None, "hgmerge")) # the old default, if found
+    tools.append((None, "internal:merge")) # internal merge as last resort
+    for p,t in tools:
+        if _findtool(ui, t) and check(t, None, symlink, binary):
+            return t
 
 def filemerge(repo, fw, fd, fo, wctx, mctx):
     """perform a 3-way merge in the working directory
@@ -27,38 +77,91 @@
         f.close()
         return name
 
-    fcm = wctx.filectx(fw)
-    fcmdata = wctx.filectx(fd).data()
+    def isbin(ctx):
+        try:
+            return util.binary(ctx.data())
+        except IOError:
+            return False
+
     fco = mctx.filectx(fo)
-
-    if not fco.cmp(fcmdata): # files identical?
+    if not fco.cmp(wctx.filectx(fd).data()): # files identical?
         return None
 
-    fca = fcm.ancestor(fco)
-    if not fca:
-        fca = repo.filectx(fw, fileid=nullrev)
+    ui = repo.ui
+    fcm = wctx.filectx(fw)
+    fca = fcm.ancestor(fco) or repo.filectx(fw, fileid=nullrev)
+    binary = isbin(fcm) or isbin(fco) or isbin(fca)
+    symlink = fcm.islink() or fco.islink()
+    tool = _picktool(repo, ui, fw, binary, symlink)
+    ui.debug(_("picked tool '%s' for %s (binary %s symlink %s)\n") %
+               (tool, fw, binary, symlink))
+
+    if not tool:
+        tool = "internal:local"
+        if ui.prompt(_(" no tool found to merge %s\n"
+                       "keep (l)ocal or take (o)ther?") % fw,
+                     _("[lo]"), _("l")) != _("l"):
+            tool = "internal:other"
+    if tool == "internal:local":
+        return 0
+    if tool == "internal:other":
+        repo.wwrite(fd, fco.data(), fco.fileflags())
+        return 0
+    if tool == "internal:fail":
+        return 1
+
+    # do the actual merge
     a = repo.wjoin(fd)
     b = temp("base", fca)
     c = temp("other", fco)
+    out = ""
+    back = a + ".orig"
+    util.copyfile(a, back)
 
     if fw != fo:
         repo.ui.status(_("merging %s and %s\n") % (fw, fo))
     else:
         repo.ui.status(_("merging %s\n") % fw)
-
     repo.ui.debug(_("my %s other %s ancestor %s\n") % (fcm, fco, fca))
 
-    cmd = (os.environ.get("HGMERGE") or repo.ui.config("ui", "merge")
-           or "hgmerge")
-    r = util.system('%s "%s" "%s" "%s"' % (cmd, a, b, c), cwd=repo.root,
-                    environ={'HG_FILE': fd,
-                             'HG_MY_NODE': str(wctx.parents()[0]),
-                             'HG_OTHER_NODE': str(mctx),
-                             'HG_MY_ISLINK': fcm.islink(),
-                             'HG_OTHER_ISLINK': fco.islink(),
-                             'HG_BASE_ISLINK': fca.islink(),})
+    # do we attempt to simplemerge first?
+    if _toolbool(ui, tool, "premerge", not (binary or symlink)):
+        r = simplemerge.simplemerge(a, b, c, quiet=True)
+        if not r:
+            ui.debug(_(" premerge successful\n"))
+            os.unlink(back)
+            os.unlink(b)
+            os.unlink(c)
+            return 0
+        util.copyfile(back, a) # restore from backup and try again
+
+    env = dict(HG_FILE=fd,
+               HG_MY_NODE=str(wctx.parents()[0]),
+               HG_OTHER_NODE=str(mctx),
+               HG_MY_ISLINK=fcm.islink(),
+               HG_OTHER_ISLINK=fco.islink(),
+               HG_BASE_ISLINK=fca.islink())
+
+    if tool == "internal:merge":
+        r = simplemerge.simplemerge(a, b, c, label=['local', 'other'])
+    else:
+        toolpath = _findtool(ui, tool)
+        args = _toolstr(ui, tool, "args", '$local $base $other')
+        if "$output" in args:
+            out, a = a, back # read input from backup, write to original
+        replace = dict(local=a, base=b, other=c, output=out)
+        args = re.sub("\$(local|base|other|output)",
+                      lambda x: '"%s"' % replace[x.group()[1:]], args)
+        r = util.system(toolpath + ' ' + args, cwd=repo.root, environ=env)
+
+    if not r and _toolbool(ui, tool, "checkconflicts"):
+        if re.match("^(<<<<<<< .*|=======|>>>>>>> .*)$", fcm.data()):
+            r = 1
+
     if r:
         repo.ui.warn(_("merging %s failed!\n") % fd)
+    else:
+        os.unlink(back)
 
     os.unlink(b)
     os.unlink(c)