diff --git a/PBGitCommit.h b/PBGitCommit.h
index 6f55b77..3e361e9 100644
--- a/PBGitCommit.h
+++ b/PBGitCommit.h
@@ -26,6 +26,7 @@ extern NSString * const kGitXCommitType;
 	NSString* details;
 	NSString *_patch;
 	NSArray* parents;
+	NSString *realSHA;
 
 	int timestamp;
 	char sign;
@@ -33,12 +34,16 @@ extern NSString * const kGitXCommitType;
 	PBGitRepository* repository;
 }
 
++ commitWithRepository:(PBGitRepository*)repo andSha:(git_oid)newSha;
 - initWithRepository:(PBGitRepository *)repo andSha:(git_oid)sha;
 
 - (void)addRef:(PBGitRef *)ref;
 - (void)removeRef:(id)ref;
+- (BOOL) hasRef:(PBGitRef *)ref;
 
 - (NSString *)realSha;
+- (BOOL) isOnSameBranchAs:(PBGitCommit *)other;
+- (BOOL) isOnHeadBranch;
 
 // <PBGitRefish>
 - (NSString *) refishName;
diff --git a/PBGitCommit.m b/PBGitCommit.m
index a8c56ad..28abcda 100644
--- a/PBGitCommit.m
+++ b/PBGitCommit.m
@@ -54,6 +54,11 @@ NSString * const kGitXCommitType = @"commit";
 	return &sha;
 }
 
++ commitWithRepository:(PBGitRepository*)repo andSha:(git_oid)newSha
+{
+	return [[[self alloc] initWithRepository:repo andSha:newSha] autorelease];
+}
+
 - initWithRepository:(PBGitRepository*) repo andSha:(git_oid)newSha
 {
 	details = nil;
@@ -64,10 +69,42 @@ NSString * const kGitXCommitType = @"commit";
 
 - (NSString *)realSha
 {
-	char *hex = git_oid_mkhex(&sha);
-	NSString *str = [NSString stringWithUTF8String:hex];
-	free(hex);
-	return str;
+	if (!realSHA) {
+		char *hex = git_oid_mkhex(&sha);
+		realSHA = [NSString stringWithUTF8String:hex];
+		free(hex);
+	}
+
+	return realSHA;
+}
+
+- (BOOL) isOnSameBranchAs:(PBGitCommit *)other
+{
+	if (!other)
+		return NO;
+
+	NSString *mySHA = [self realSha];
+	NSString *otherSHA = [other realSha];
+
+	if ([otherSHA isEqualToString:mySHA])
+		return YES;
+
+	NSString *commitRange = [NSString stringWithFormat:@"%@..%@", mySHA, otherSHA];
+	NSString *parentsOutput = [repository outputForArguments:[NSArray arrayWithObjects:@"rev-list", @"--parents", @"-1", commitRange, nil]];
+	if ([parentsOutput isEqualToString:@""]) {
+		return NO;
+	}
+
+	NSString *mergeSHA = [repository outputForArguments:[NSArray arrayWithObjects:@"merge-base", mySHA, otherSHA, nil]];
+	if ([mergeSHA isEqualToString:mySHA] || [mergeSHA isEqualToString:otherSHA])
+		return YES;
+
+	return NO;
+}
+
+- (BOOL) isOnHeadBranch
+{
+	return [self isOnSameBranchAs:[repository headCommit]];
 }
 
 // FIXME: Remove this method once it's unused.
@@ -108,6 +145,18 @@ NSString * const kGitXCommitType = @"commit";
 	[self.refs removeObject:ref];
 }
 
+- (BOOL) hasRef:(PBGitRef *)ref
+{
+	if (!self.refs)
+		return NO;
+
+	for (PBGitRef *existingRef in self.refs)
+		if ([existingRef isEqualToRef:ref])
+			return YES;
+
+	return NO;
+}
+
 - (NSMutableArray *)refs
 {
 	return [[repository refs] objectForKey:[self realSha]];
diff --git a/PBGitRepository.h b/PBGitRepository.h
index 93c38c9..c8bd680 100644
--- a/PBGitRepository.h
+++ b/PBGitRepository.h
@@ -14,6 +14,7 @@
 extern NSString* PBGitRepositoryErrorDomain;
 
 @class PBGitWindowController;
+@class PBGitCommit;
 
 @interface PBGitRepository : NSDocument {
 	PBGitRevList* revisionList;
@@ -51,6 +52,15 @@ extern NSString* PBGitRepositoryErrorDomain;
 - (void) addRef:(PBGitRef *)ref fromParameters:(NSArray *)params;
 - (void) lazyReload;
 - (PBGitRevSpecifier*) headRef;
+- (NSString *) headSHA;
+- (PBGitCommit *) headCommit;
+- (NSString *) shaForRef:(PBGitRef *)ref;
+- (PBGitCommit *) commitForRef:(PBGitRef *)ref;
+- (PBGitCommit *) commitForSHA:(NSString *)sha;
+- (BOOL) isSHAOnHeadBranch:(NSString *)testSHA;
+- (BOOL) isRefOnHeadBranch:(PBGitRef *)testRef;
+- (BOOL) checkRefFormat:(NSString *)refName;
+- (BOOL) refExists:(PBGitRef *)ref;
 
 - (void) readCurrentBranch;
 - (PBGitRevSpecifier*) addBranch: (PBGitRevSpecifier*) rev;
diff --git a/PBGitRepository.m b/PBGitRepository.m
index 2e74040..477d15b 100644
--- a/PBGitRepository.m
+++ b/PBGitRepository.m
@@ -281,6 +281,105 @@ NSString* PBGitRepositoryErrorDomain = @"GitXErrorDomain";
 
 	return _headRef;
 }
+
+- (NSString *) headSHA
+{
+	return [self shaForRef:[[self headRef] ref]];
+}
+
+- (PBGitCommit *) headCommit
+{
+	return [self commitForSHA:[self headSHA]];
+}
+
+- (NSString *) shaForRef:(PBGitRef *)ref
+{
+	if (!ref)
+		return nil;
+
+	for (NSString *sha in refs)
+		for (PBGitRef *existingRef in [refs objectForKey:sha])
+			if ([existingRef isEqualToRef:ref])
+				return sha;
+
+	int retValue = 1;
+	NSArray *args = [NSArray arrayWithObjects:@"rev-list", @"-1", [ref ref], nil];
+	NSString *shaForRef = [self outputInWorkdirForArguments:args retValue:&retValue];
+	if (retValue || [shaForRef isEqualToString:@""])
+		return nil;
+
+	return shaForRef;
+}
+
+- (PBGitCommit *) commitForRef:(PBGitRef *)ref
+{
+	if (!ref)
+		return nil;
+
+	return [self commitForSHA:[self shaForRef:ref]];
+}
+
+- (PBGitCommit *) commitForSHA:(NSString *)sha
+{
+	if (!sha)
+		return nil;
+	NSArray *revList = [self.revisionList.commits copy];
+
+	for (PBGitCommit *commit in revList)
+		if ([[commit realSha] isEqualToString:sha])
+			return commit;
+
+	return nil;
+}
+
+- (BOOL) isSHAOnHeadBranch:(NSString *)testSHA
+{
+	if (!testSHA)
+		return NO;
+
+	NSString *headSHA = [self headSHA];
+
+	if ([testSHA isEqualToString:headSHA])
+		return YES;
+
+	NSString *commitRange = [NSString stringWithFormat:@"%@..%@", testSHA, headSHA];
+	NSString *parentsOutput = [self outputForArguments:[NSArray arrayWithObjects:@"rev-list", @"--parents", @"-1", commitRange, nil]];
+	if ([parentsOutput isEqualToString:@""]) {
+		return NO;
+	}
+
+	NSString *mergeSHA = [self outputForArguments:[NSArray arrayWithObjects:@"merge-base", testSHA, headSHA, nil]];
+	if ([mergeSHA isEqualToString:testSHA] || [mergeSHA isEqualToString:headSHA])
+		return YES;
+
+	return NO;
+}
+
+- (BOOL) isRefOnHeadBranch:(PBGitRef *)testRef
+{
+	if (!testRef)
+		return NO;
+
+	return [self isSHAOnHeadBranch:[self shaForRef:testRef]];
+}
+
+- (BOOL) checkRefFormat:(NSString *)refName
+{
+	int retValue = 1;
+	[self outputInWorkdirForArguments:[NSArray arrayWithObjects:@"check-ref-format", refName, nil] retValue:&retValue];
+	if (retValue)
+		return NO;
+	return YES;
+}
+
+- (BOOL) refExists:(PBGitRef *)ref
+{
+	int retValue = 1;
+    NSString *output = [self outputInWorkdirForArguments:[NSArray arrayWithObjects:@"for-each-ref", [ref ref], nil] retValue:&retValue];
+    if (retValue || [output isEqualToString:@""])
+        return NO;
+    return YES;
+}
 		
 // Returns either this object, or an existing, equal object
 - (PBGitRevSpecifier*) addBranch: (PBGitRevSpecifier*) rev
diff --git a/PBGitRevSpecifier.h b/PBGitRevSpecifier.h
index 0461908..bc2724c 100644
--- a/PBGitRevSpecifier.h
+++ b/PBGitRevSpecifier.h
@@ -20,10 +20,13 @@
 
 - (BOOL) isSimpleRef;
 - (NSString*) simpleRef;
+- (PBGitRef *) ref;
 - (BOOL) hasPathLimiter;
 - (BOOL) hasLeftRight;
 
 - (BOOL) isEqualTo: (PBGitRevSpecifier*) other;
+- (BOOL) isAllBranchesRev;
+- (BOOL) isLocalBranchesRev;
 
 + (PBGitRevSpecifier *)allBranchesRevSpec;
 + (PBGitRevSpecifier *)localBranchesRevSpec;
diff --git a/PBGitRevSpecifier.m b/PBGitRevSpecifier.m
index 0fe9093..529275d 100644
--- a/PBGitRevSpecifier.m
+++ b/PBGitRevSpecifier.m
@@ -59,6 +59,14 @@
 	return [parameters objectAtIndex:0];
 }
 
+- (PBGitRef *) ref
+{
+	if (![self isSimpleRef])
+		return nil;
+
+	return [PBGitRef refFromString:[self simpleRef]];
+}
+
 - (NSString*) description
 {
 	if (description)
@@ -95,6 +103,16 @@
 			 (!description  || [description isEqualToString:other.description]));
 }
 
+- (BOOL) isAllBranchesRev
+{
+	return [self isEqualTo:[PBGitRevSpecifier allBranchesRevSpec]];
+}
+
+- (BOOL) isLocalBranchesRev
+{
+	return [self isEqualTo:[PBGitRevSpecifier localBranchesRevSpec]];
+}
+
 - (void) encodeWithCoder:(NSCoder *)coder
 {
 	[coder encodeObject:description forKey:@"Description"];