Added support for Mercurial to the plugin.

Basically this just removes the unconditional reliance on the
git executable for the diff3 checking and introduces the
variable `g:diffconflicts_vcs` to decide whether to call git
or not.
Aside from this small change there is just the documentation
added on how to utilize this plugin in Mercurial.

Author: Harald Klimach

README.md

@@ -1,6 +1,6 @@
 # vim-diffconflicts
 
-A better Vimdiff Git mergetool
+A better Vimdiff Git (and Mercurial)  mergetool
 
 tl;dr:
 
@@ -91,3 +91,26 @@ splitting them apart.
     changes.
 
     This tab is not opened by default so that Vim starts more quickly.
+
+
+## Mercurial
+
+Configure Mercurial to use diffconflicts as a mergetool by adding:
+
+    ```
+    [merge-tools]
+    diffconflicts.executable=vim
+    diffconflicts.args=-c 'let g:diffconflicts_vcs="hg"' -c DiffConflicts "$output" "$base" "$local" "$other"
+    diffconflicts.premerge=keep
+    diffconflicts.check=conflicts
+    diffconflicts.priority=99
+    ```
+
+to your `.hgrc` file.
+Or, if you prefer to always open both the diff view and the history view use
+
+    ```
+    diffconflicts.args=-c 'let g:diffconflicts_vcs="hg"' -c DiffConflictsWithHistory "$output" "$base" "$local" "$other"
+    ```
+
+as the args setting to call `DiffConflictsWithHistory`.

_utils/make-conflicts_hg.sh

@@ -0,0 +1,53 @@
+#!/bin/sh
+
+hg init testrepo_hg
+cd testrepo_hg
+
+cat << EOF > poem.txt
+twas bri1lig, and the slithy toves
+did gyre and gimble in the wabe
+all mimsy were the borogroves
+and the m0me raths outgabe.
+
+"Beware the Jabberwock, my son!
+The jaws that bite, the claws that catch!
+Beware the Jub jub bird, and shun
+The frumious bandersnatch!"
+EOF
+
+hg add poem.txt
+hg bookmark master
+hg commit -m 'Commit One'
+
+cat << EOF > poem.txt
+twas brillig, and the slithy toves
+Did gyre and gimble in the wabe:
+all mimsy were the borogoves,
+And the mome raths outgrabe.
+
+"Beware the Jabberwock, my son!
+The jaws that bite, the claws that catch!
+Beware the Jubjub bird, and shun
+The frumious Bandersnatch!"
+EOF
+
+hg bookmark branchA
+hg commit -m 'Fix syntax mistakes'
+
+hg update -Cr master
+
+cat << EOF > poem.txt
+'Twas brillig, and the slithy toves
+Did gyre and gimble in the wabe:
+All mimsy were the borogroves
+And the mome raths outgabe.
+
+"Beware the Jabberwock, my son!
+The jaws that bite, the claws that catch!
+Beware the Jub jub bird, and shun
+The frumious bandersnatch!"
+EOF
+
+hg commit -m 'Buncha fixes'
+
+hg --config ui.merge=internal:merge merge branchA

doc/diffconflicts.txt

@@ -1,4 +1,4 @@
-*diffconflicts.txt*	A better Vimdiff Git mergetool
+*diffconflicts.txt*	A better Vimdiff Git/Mercurial mergetool
 
 This plugin converts a file containing Git conflict markers into a two-way diff
 in Vimdiff. Additional mappings can be given to see the full three-way diff.
@@ -10,6 +10,14 @@ git config --global mergetool.diffconflicts.cmd 'vim -c DiffConflicts "$MERGED"
 git config --global mergetool.diffconflicts.trustExitCode true
 git config --global mergetool.keepBackup false
 
+For Mercurial use the following settings in your .hgrc:
+
+[merge-tools]
+diffconflicts.executable=vim
+diffconflicts.args=-c 'let g:diffconflicts_vcs="hg"' -c DiffConflicts "$output" "$base" "$local" "$other"
+diffconflicts.premerge=keep
+diffconflicts.check=conflicts
+
 Commands:
 :DiffConflicts
 	Convert a file containing Git conflict markers into a two-way diff.
@@ -23,4 +31,5 @@ Commands:
 	the Git mergetool configuration to always open the history by default.
 
 						*DiffConflicts-settings*
-This plugin doesn't have any settings.
+        Use g:diffconflicts_vcs to indicate which version control system produced
+        the conflict file (Git or Mercurial).

plugin/diffconflicts.vim

@@ -10,6 +10,13 @@ let g:loaded_diffconflicts = 1
 let s:save_cpo = &cpo
 set cpo&vim
 
+" CONFIGURATION
+if !exists("g:diffconflicts_vcs")
+    " Default to git
+    let g:diffconflicts_vcs = "git"
+endif
+
+let g:loaded_diffconflicts = 1
 function! s:hasConflicts()
     try
         silent execute "%s/^<<<<<<< //gn"
@@ -22,7 +29,14 @@ endfunction
 function! s:diffconfl()
     let l:origBuf = bufnr("%")
     let l:origFt = &filetype
-    let l:conflictStyle = system("git config --get merge.conflictStyle")[:-2]
+
+    if g:diffconflicts_vcs == "git"
+        " Obtain the git setting for the conflict style.
+        let l:conflictStyle = system("git config --get merge.conflictStyle")[:-2]
+    else
+        " Assume 2way conflict style otherwise.
+        let l:conflictStyle = "diff"
+    endif
 
     " Set up the right-hand side.
     rightb vsplit