Refactor exec of a command and reading one line into utility

Change-Id: Ia9e5afe7f29c3e5e74b8d226441ed429fb229c82
Signed-off-by: Robin Rosenberg <robin.rosenberg@dewire.com>

org.eclipse.jgit/src/org/eclipse/jgit/util/FS.java

@@ -43,7 +43,10 @@
 
 package org.eclipse.jgit.util;
 
+import java.io.BufferedReader;
 import java.io.File;
+import java.io.IOException;
+import java.io.InputStreamReader;
 import java.security.AccessController;
 import java.security.PrivilegedAction;
 
@@ -210,4 +213,43 @@ public abstract class FS {
 		}
 		return null;
 	}
+
+	/**
+	 * Execute a command and return a single line of output as a String
+	 *
+	 * @param dir
+	 *            Working directory for the command
+	 * @param command
+	 *            as component array
+	 * @param encoding
+	 * @return the one-line output of the command
+	 */
+	protected static String readPipe(File dir, String[] command, String encoding) {
+		try {
+			final Process p = Runtime.getRuntime().exec(command, null, dir);
+			final BufferedReader lineRead = new BufferedReader(
+					new InputStreamReader(p.getInputStream(), encoding));
+			String r = null;
+			try {
+				r = lineRead.readLine();
+			} finally {
+				p.getOutputStream().close();
+				p.getErrorStream().close();
+				lineRead.close();
+			}
+
+			for (;;) {
+				try {
+					if (p.waitFor() == 0 && r != null && r.length() > 0)
+						return r;
+					break;
+				} catch (InterruptedException ie) {
+					// Stop bothering me, I have a zombie to reap.
+				}
+			}
+		} catch (IOException e) {
+			// ignore
+		}
+		return null;
+	}
 }

org.eclipse.jgit/src/org/eclipse/jgit/util/FS_Win32_Cygwin.java

@@ -43,10 +43,7 @@
 
 package org.eclipse.jgit.util;
 
-import java.io.BufferedReader;
 import java.io.File;
-import java.io.IOException;
-import java.io.InputStreamReader;
 import java.security.AccessController;
 import java.security.PrivilegedAction;
 
@@ -69,36 +66,11 @@ class FS_Win32_Cygwin extends FS_Win32 {
 	}
 
 	public File resolve(final File dir, final String pn) {
-		try {
-			final Process p;
-
-			p = Runtime.getRuntime().exec(
-					new String[] { cygpath, "--windows", "--absolute", pn },
-					null, dir);
-			p.getOutputStream().close();
-
-			final BufferedReader lineRead = new BufferedReader(
-					new InputStreamReader(p.getInputStream(), "UTF-8"));
-			String r = null;
-			try {
-				r = lineRead.readLine();
-			} finally {
-				lineRead.close();
-			}
-
-			for (;;) {
-				try {
-					if (p.waitFor() == 0 && r != null && r.length() > 0)
-						return new File(r);
-					break;
-				} catch (InterruptedException ie) {
-					// Stop bothering me, I have a zombie to reap.
-				}
-			}
-		} catch (IOException ioe) {
-			// Fall through and use the default return.
-			//
-		}
+		String w = readPipe(dir, //
+				new String[] { cygpath, "--windows", "--absolute", pn }, //
+				"UTF-8");
+		if (w != null)
+			return new File(w);
 		return super.resolve(dir, pn);
 	}