doc&tools: Add murge script, for analyzing 3 way conflicts.

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

doc/libav-merge.txt

@@ -103,6 +103,10 @@ It has two modes: merge, and noop. The noop mode creates a merge with no change
 to the HEAD. You can pass a hash as extra argument to reference a justification
 (it is common that we already have the change done in FFmpeg).
 
+Also see tools/murge, you can copy and paste a 3 way conflict into its stdin
+and it will display colored diffs. Any arguments to murge (like ones to suppress
+whitespace differences) are passed into colordiff.
+
 TODO/FIXME/UNMERGED
 ===================
 

tools/murge

@@ -0,0 +1,11 @@
+#!/bin/sh
+
+grep -A99999 '^<<<<<<<' | grep -B99999 '^>>>>>>>' >murge.X
+grep -A99999 '^====' murge.X | egrep -v '^(=======|<<<<<<<|>>>>>>>|\|\|\|\|\|\|\|)' >murge.theirs
+grep -B99999 '^||||' murge.X | egrep -v '^(=======|<<<<<<<|>>>>>>>|\|\|\|\|\|\|\|)' >murge.ours
+grep -B99999 '^====' murge.X | grep -A99999 '^||||' | egrep -v '^(=======|<<<<<<<|>>>>>>>|\|\|\|\|\|\|\|)'  >murge.common
+
+colordiff -du $* murge.ours murge.theirs
+grep . murge.common > /dev/null && colordiff -du $* murge.common murge.theirs
+grep . murge.common > /dev/null && colordiff -du $* murge.common murge.ours
+rm murge.theirs murge.common murge.ours murge.X