Parse merge conflict format for multi diffs.

dart/tests/try/poi/source_update.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library trydart.source_update;
 
 /// Returns [updates] expanded to full compilation units/source files.
 ///
 /// [updates] is a convenient way to write updates/patches to a single source
 /// file without repeating common parts.
@@ skipping 22 matching lines @@
     } else {
       for (StringBuffer buffer in result) {
         buffer.write(chunk);
       }
     }
   }
 
   return result.map((e) => '$e').toList();
 }
 
-/// Returns [files] split into mulitple named files. The keys in the returned
+/// Returns [files] split into multiple named files. The keys in the returned
 /// map are filenames, the values are the files' content.
 ///
 /// Names are indicated by a line on the form "==> filename <==". Spaces are
 /// significant. For example, given this input:
 ///
 ///     ==> file1.dart <==
 ///     First line of file 1.
 ///     Second line of file 1.
 ///     Third line of file 1.
 ///     ==> empty.dart <==
@@ skipping 51 matching lines @@
   finishFile();
   return result;
 }
 
 /// Split [text] into lines preserving trailing newlines (unlike
 /// String.split("\n"). Also, if [text] is empty, return an empty list (unlike
 /// String.split("\n")).
 List<String> splitLines(String text) {
   return text.split(new RegExp('^', multiLine: true));
 }
+
+/// Expand a file with diffs in common merge conflict format into a [List] that
+/// can be passed to [expandUpdates].
+///
+/// For example:
+///     first
+///     <<<<<<<
+///     v1
+///     =======
+///     v2
+///     =======
+///     v3
+///     >>>>>>>
+///     last
+///
+/// Would be expanded to something equivalent to:
+///
+///     ["first\n", ["v1\n", "v2\n", "v3\n"], "last\n"]
+List expandDiff(String text) {
+  List result = [new StringBuffer()];
+  bool inDiff = false;
+  for (String line in splitLines(text)) {
+    if (inDiff) {
+      if (line.startsWith("=======")) {
+        result.last.add(new StringBuffer());
+      } else if (line.startsWith(">>>>>>>")) {
+        inDiff = false;
+        result.add(new StringBuffer());
+      } else {
+        result.last.last.write(line);
+      }
+    } else if (line.startsWith("<<<<<<<")) {
+      inDiff = true;
+      result.add(<StringBuffer>[new StringBuffer()]);
+    } else {
+      result.last.write(line);
+    }
+  }
+  return result;
+}