Update from Google.

--
MOE_MIGRATED_REVID=85702957
diff --git a/src/main/java/com/google/devtools/build/lib/shell/ShellUtils.java b/src/main/java/com/google/devtools/build/lib/shell/ShellUtils.java
new file mode 100644
index 0000000..5157f34
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/shell/ShellUtils.java
@@ -0,0 +1,145 @@
+// Copyright 2014 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.devtools.build.lib.shell;
+
+import java.util.List;
+
+/**
+ * Utility functions for Bourne shell commands, including escaping and
+ * tokenizing.
+ */
+public abstract class ShellUtils {
+
+  private ShellUtils() {}
+
+  /**
+   * Characters that have no special meaning to the shell.
+   */
+  private static final String SAFE_PUNCTUATION = "@%-_+:,./";
+
+  /**
+   * Quotes a word so that it can be used, without further quoting,
+   * as an argument (or part of an argument) in a shell command.
+   */
+  public static String shellEscape(String word) {
+    int len = word.length();
+    if (len == 0) {
+      // Empty string is a special case: needs to be quoted to ensure that it gets
+      // treated as a separate argument.
+      return "''";
+    }
+    for (int ii = 0; ii < len; ii++) {
+      char c = word.charAt(ii);
+      // We do this positively so as to be sure we don't inadvertently forget
+      // any unsafe characters.
+      if (!Character.isLetterOrDigit(c) && SAFE_PUNCTUATION.indexOf(c) == -1) {
+        // replace() actually means "replace all".
+        return "'" + word.replace("'", "'\\''") + "'";
+      }
+    }
+    return word;
+  }
+
+  /**
+   * Given an argv array such as might be passed to execve(2), returns a string
+   * that can be copied and pasted into a Bourne shell for a similar effect.
+   */
+  public static String prettyPrintArgv(List<String> argv) {
+    StringBuilder buf = new StringBuilder();
+    for (String arg: argv) {
+      if (buf.length() > 0) {
+        buf.append(' ');
+      }
+      buf.append(shellEscape(arg));
+    }
+    return buf.toString();
+  }
+
+
+  /**
+   * Thrown by tokenize method if there is an error
+   */
+  public static class TokenizationException extends Exception {
+    TokenizationException(String message) {
+      super(message);
+    }
+  }
+
+  /**
+   * Populates the passed list of command-line options extracted from {@code
+   * optionString}, which is a string containing multiple options, delimited in
+   * a Bourne shell-like manner.
+   *
+   * @param options the list to be populated with tokens.
+   * @param optionString the string to be tokenized.
+   * @throws TokenizationException if there was an error (such as an
+   * unterminated quotation).
+   */
+  public static void tokenize(List<String> options, String optionString)
+      throws TokenizationException {
+    // See test suite for examples.
+    //
+    // Note: backslash escapes the following character, except within a
+    // single-quoted region where it is literal.
+
+    StringBuilder token = new StringBuilder();
+    boolean forceToken = false;
+    char quotation = '\0'; // NUL, '\'' or '"'
+    for (int ii = 0, len = optionString.length(); ii < len; ii++) {
+      char c = optionString.charAt(ii);
+      if (quotation != '\0') { // in quotation
+        if (c == quotation) { // end of quotation
+          quotation = '\0';
+        } else if (c == '\\' && quotation == '"') { // backslash in "-quotation
+          if (++ii == len) {
+            throw new TokenizationException("backslash at end of string");
+          }
+          c = optionString.charAt(ii);
+          if (c != '\\' && c != '"') {
+            token.append('\\');
+          }
+          token.append(c);
+        } else { // regular char, in quotation
+          token.append(c);
+        }
+      } else { // not in quotation
+        if (c == '\'' || c == '"') { // begin single/double quotation
+          quotation = c;
+          forceToken = true;
+        } else if (c == ' ' || c == '\t') { // space, not quoted
+          if (forceToken || token.length() > 0) {
+            options.add(token.toString());
+            token = new StringBuilder();
+            forceToken = false;
+          }
+        } else if (c == '\\') { // backslash, not quoted
+          if (++ii == len) {
+            throw new TokenizationException("backslash at end of string");
+          }
+          token.append(optionString.charAt(ii));
+        } else { // regular char, not quoted
+          token.append(c);
+        }
+      }
+    }
+    if (quotation != '\0') {
+      throw new TokenizationException("unterminated quotation");
+    }
+    if (forceToken || token.length() > 0) {
+      options.add(token.toString());
+    }
+  }
+
+}