Fix QuotedString.GIT_PATH escaping rules

We shouldn't escape non-special ASCII characters such as '@' or '~'.
These are valid in a path name on POSIX systems, and may appear as
part of a path in a GNU or Git style patch script.  Escaping them
into octal just obfuscates the user's intent, with no gain.

When parsing an escaped octal sequence, we must parse no more
than 3 digits.  That is, "\1002" is actually "@2", not the Unicode
character \u0202.

Change-Id: I3a849a0d318e69b654f03fd559f5d7f99dd63e5c
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

org.eclipse.jgit.test/tst/org/eclipse/jgit/util/QuotedStringGitPathStyleTest.java

@@ -153,7 +153,7 @@ public class QuotedStringGitPathStyleTest extends TestCase {
 
 	public void testQuote_OctalAll() {
 		assertQuote("\\001", "\1");
-		assertQuote("\\176", "~");
+		assertQuote("\\177", "\u007f");
 		assertQuote("\\303\\277", "\u00ff"); // \u00ff in UTF-8
 	}
 
@@ -184,4 +184,9 @@ public class QuotedStringGitPathStyleTest extends TestCase {
 	public void testQuote_Ang() {
 		assertQuote("\\303\\205ngstr\\303\\266m", "\u00c5ngstr\u00f6m");
 	}
+
+	public void testQuoteAtAndNumber() {
+		assertSame("abc@2x.png", GIT_PATH.quote("abc@2x.png"));
+		assertDequote("abc@2x.png", "abc\\1002x.png");
+	}
 }

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

@@ -222,14 +222,24 @@ public abstract class QuotedString {
 			for (int i = 'A'; i <= 'Z'; i++)
 				quote[i] = 0;
 			quote[' '] = 0;
+			quote['$'] = 0;
+			quote['%'] = 0;
+			quote['&'] = 0;
+			quote['*'] = 0;
 			quote['+'] = 0;
 			quote[','] = 0;
 			quote['-'] = 0;
 			quote['.'] = 0;
 			quote['/'] = 0;
+			quote[':'] = 0;
+			quote[';'] = 0;
 			quote['='] = 0;
+			quote['?'] = 0;
+			quote['@'] = 0;
 			quote['_'] = 0;
 			quote['^'] = 0;
+			quote['|'] = 0;
+			quote['~'] = 0;
 
 			quote['\u0007'] = 'a';
 			quote['\b'] = 'b';
@@ -335,7 +345,7 @@ public abstract class QuotedString {
 				case '2':
 				case '3': {
 					int cp = in[inPtr - 1] - '0';
-					while (inPtr < inEnd) {
+					for (int n = 1; n < 3 && inPtr < inEnd; n++) {
 						final byte c = in[inPtr];
 						if ('0' <= c && c <= '7') {
 							cp <<= 3;