Add hidden preference to use a split column guide in commit messages

The conventional git commit message styling says to limit your first line
to roughly 50 characters, and subsequent lines to 76 characters. The column
guide in GitX doesn't support this.

Implement 2 new hidden preferences, one to determine whether it uses a split
column guide and the other to set the length of this guide. Default these
preferences to NO and 76, respectively. When the split column guide is
turned on, the drawing code will draw the normal column guide only for the
first line and it will use the split column guide length for every other
line.

PBCommitMessageView.m

@@ -18,16 +18,33 @@ - (void)drawRect:(NSRect)aRect
 	// draw a vertical line after the given size (used as an indicator
 	// for the first line of the commit message)
     if ([PBGitDefaults commitMessageViewHasVerticalLine]) {
-        float characterWidth = [@" " sizeWithAttributes:[self typingAttributes]].width;
-        float lineWidth = characterWidth * [PBGitDefaults commitMessageViewVerticalLineLength];
+        NSSize characterSize = [@" " sizeWithAttributes:[self typingAttributes]];
+        float lineWidth = characterSize.width * [PBGitDefaults commitMessageViewVerticalLineLength];
 
         [[NSColor lightGrayColor] set];
         float padding = [[self textContainer] lineFragmentPadding];
         NSRect line;
         line.origin.x = padding + lineWidth;
         line.origin.y = 0;
         line.size.width = 1;
-        line.size.height = [self bounds].size.height;
+		if ([PBGitDefaults commitMessageViewHasSplitVerticalLine]) {
+			line.size.height = characterSize.height;
+			NSRectFill(line);
+			line.origin.y = characterSize.height;
+			lineWidth = characterSize.width * [PBGitDefaults commitMessageViewSplitVerticalLineLength];
+			line.size.width = padding + lineWidth - line.origin.x;
+			line.size.height = 1;
+			if (line.size.width < 0) {
+				line.origin.x = padding + lineWidth + 1;
+				line.size.width = -line.size.width;
+			}
+			NSRectFill(line);
+			line.origin.x = padding + lineWidth;
+			line.size.width = 1;
+			line.size.height = [self bounds].size.height - characterSize.height;
+		} else {
+			line.size.height = [self bounds].size.height;
+		}
         NSRectFill(line);
     }
 }

PBGitDefaults.h

@@ -13,6 +13,8 @@
 
 + (int) commitMessageViewVerticalLineLength;
 + (BOOL) commitMessageViewHasVerticalLine;
++ (int) commitMessageViewSplitVerticalLineLength;
++ (BOOL) commitMessageViewHasSplitVerticalLine;
 + (BOOL) isGistEnabled;
 + (BOOL) isGravatarEnabled;
 + (BOOL) confirmPublicGists;

PBGitDefaults.m

@@ -10,8 +10,11 @@
 #import "PBHistorySearchController.h"
 
 #define kDefaultVerticalLineLength 50
+#define kDefaultSplitVerticalLineLength 76
 #define kCommitMessageViewVerticalLineLength @"PBCommitMessageViewVerticalLineLength"
 #define kCommitMessageViewHasVerticalLine @"PBCommitMessageViewHasVerticalLine"
+#define kCommitMessageViewHasSplitVerticalLine @"PBCommitMessageViewHasSplitVerticalLine"
+#define kCommitMessageViewSplitVerticalLineLength @"PBCommitMessageViewSplitVerticalLineLength"
 #define kEnableGist @"PBEnableGist"
 #define kEnableGravatar @"PBEnableGravatar"
 #define kConfirmPublicGists @"PBConfirmPublicGists"
@@ -37,6 +40,10 @@ + (void)initialize
                       forKey:kCommitMessageViewVerticalLineLength];
     [defaultValues setObject:[NSNumber numberWithBool:YES]
                       forKey:kCommitMessageViewHasVerticalLine];
+	[defaultValues setObject:[NSNumber numberWithInt:kDefaultSplitVerticalLineLength]
+					  forKey:kCommitMessageViewSplitVerticalLineLength];
+	[defaultValues setObject:[NSNumber numberWithBool:NO]
+					  forKey:kCommitMessageViewHasSplitVerticalLine];
 	[defaultValues setObject:[NSNumber numberWithBool:YES]
 			  forKey:kEnableGist];
 	[defaultValues setObject:[NSNumber numberWithBool:YES]
@@ -70,6 +77,16 @@ + (BOOL) commitMessageViewHasVerticalLine
 	return [[NSUserDefaults standardUserDefaults] boolForKey:kCommitMessageViewHasVerticalLine];
 }
 
++ (int) commitMessageViewSplitVerticalLineLength
+{
+	return [[NSUserDefaults standardUserDefaults] integerForKey:kCommitMessageViewSplitVerticalLineLength];
+}
+
++ (BOOL) commitMessageViewHasSplitVerticalLine
+{
+	return [[NSUserDefaults standardUserDefaults] boolForKey:kCommitMessageViewHasSplitVerticalLine];
+}
+
 + (BOOL) isGistEnabled
 {
 	return [[NSUserDefaults standardUserDefaults] boolForKey:kEnableGist];