Make false/true into builtins

Making `true` into a builtin is a significant optimization to `while
true` loops. As long as `true` is a builtin, we may as well make `false`
builtin as well (despite the fact that it's not typically executed in a
loop).

builtin.cpp

@@ -4001,6 +4001,16 @@ int builtin_parse(parser_t &parser, wchar_t **argv)
     return STATUS_BUILTIN_OK;
 }
 
+int builtin_true(parser_t &parser, wchar_t **argv)
+{
+    return STATUS_BUILTIN_OK;
+}
+
+int builtin_false(parser_t &parser, wchar_t **argv)
+{
+    return STATUS_BUILTIN_ERROR;
+}
+
 /*
   END OF BUILTIN COMMANDS
   Below are functions for handling the builtin commands.
@@ -4038,6 +4048,7 @@ static const builtin_data_t builtin_datas[]=
     { 		L"end",  &builtin_generic, N_(L"End a block of commands")   },
     { 		L"exec",  &builtin_generic, N_(L"Run command in current process")  },
     { 		L"exit",  &builtin_exit, N_(L"Exit the shell") },
+    { 		L"false",  &builtin_false, N_(L"Return an unsuccessful result") },
     { 		L"fg",  &builtin_fg, N_(L"Send job to foreground")   },
     { 		L"for",  &builtin_generic, N_(L"Perform a set of commands multiple times")   },
     { 		L"function",  &builtin_generic, N_(L"Define a new function")   },
@@ -4058,6 +4069,7 @@ static const builtin_data_t builtin_datas[]=
     { 		L"status",  &builtin_status, N_(L"Return status information about fish")  },
     { 		L"switch",  &builtin_generic, N_(L"Conditionally execute a block of commands")   },
     { 		L"test",  &builtin_test, N_(L"Test a condition")   },
+    { 		L"true",  &builtin_true, N_(L"Return a successful result") },
     { 		L"ulimit",  &builtin_ulimit, N_(L"Set or get the shells resource usage limits")  },
     { 		L"while",  &builtin_generic, N_(L"Perform a command multiple times")   }
 };

doc_src/false.txt

@@ -0,0 +1,10 @@
+\section false false - return an unsuccessful result
+
+\subsection false-synopsis Synopsis
+\fish{synopsis}
+false
+\endfish
+
+\subsection false-description Description
+
+`false` sets the exit status to 1.

doc_src/true.txt

@@ -0,0 +1,10 @@
+\section true true - return a successful result
+
+\subsection true-synopsis Synopsis
+\fish{synopsis}
+true
+\endfish
+
+\subsection true-description Description
+
+`true` sets the exit status to 0.

fish.xcodeproj/project.pbxproj

@@ -171,8 +171,8 @@
 		D0F019FD15A977CA0034B3B1 /* config.fish in CopyFiles */ = {isa = PBXBuildFile; fileRef = D0C4FD9415A7D7EE00212EF1 /* config.fish */; };
 		D0F01A0315A978910034B3B1 /* osx_fish_launcher.m in Sources */ = {isa = PBXBuildFile; fileRef = D0D02AFA159871B2008E62BD /* osx_fish_launcher.m */; };
 		D0F01A0515A978A10034B3B1 /* Foundation.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = D0CBD583159EEE010024809C /* Foundation.framework */; };
-                D0F5B46519CFCDE80090665E /* wcstringutil.cpp in Sources */ = {isa = PBXBuildFile; fileRef = D0F5B46319CFCDE80090665E /* wcstringutil.cpp */; };
+		D0F5B46519CFCDE80090665E /* wcstringutil.cpp in Sources */ = {isa = PBXBuildFile; fileRef = D0F5B46319CFCDE80090665E /* wcstringutil.cpp */; };
-                D0F5B46619CFCEBC0090665E /* wcstringutil.cpp in Sources */ = {isa = PBXBuildFile; fileRef = D0F5B46319CFCDE80090665E /* wcstringutil.cpp */; };
+		D0F5B46619CFCEBC0090665E /* wcstringutil.cpp in Sources */ = {isa = PBXBuildFile; fileRef = D0F5B46319CFCDE80090665E /* wcstringutil.cpp */; };
 		D0FE8EE8179FB760008C9F21 /* parse_productions.cpp in Sources */ = {isa = PBXBuildFile; fileRef = D0FE8EE7179FB75F008C9F21 /* parse_productions.cpp */; };
 /* End PBXBuildFile section */
 
@@ -456,8 +456,8 @@
 		D0D2693C159835CA005D9B9C /* fish */ = {isa = PBXFileReference; explicitFileType = "compiled.mach-o.executable"; includeInIndex = 0; path = fish; sourceTree = BUILT_PRODUCTS_DIR; };
 		D0D9B2B318555D92001AE279 /* parse_constants.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = parse_constants.h; sourceTree = "<group>"; };
 		D0F3373A1506DE3C00ECEFC0 /* builtin_test.cpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.cpp; path = builtin_test.cpp; sourceTree = "<group>"; };
-                D0F5B46319CFCDE80090665E /* wcstringutil.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = wcstringutil.cpp; sourceTree = "<group>"; };
+		D0F5B46319CFCDE80090665E /* wcstringutil.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = wcstringutil.cpp; sourceTree = "<group>"; };
-                D0F5B46419CFCDE80090665E /* wcstringutil.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = wcstringutil.h; sourceTree = "<group>"; };
+		D0F5B46419CFCDE80090665E /* wcstringutil.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = wcstringutil.h; sourceTree = "<group>"; };
 		D0F5E28415A7A32D00315DFF /* config.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = config.h; sourceTree = "<group>"; };
 		D0FE8EE6179CA8A5008C9F21 /* parse_productions.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = parse_productions.h; sourceTree = "<group>"; };
 		D0FE8EE7179FB75F008C9F21 /* parse_productions.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = parse_productions.cpp; sourceTree = "<group>"; };
@@ -644,8 +644,8 @@
 				D0C9733718DE5449002D7C81 /* utf8.cpp */,
 				D0A0852613B3ACEE0099B651 /* util.h */,
 				D0A0855E13B3ACEE0099B651 /* util.cpp */,
-                                D0F5B46419CFCDE80090665E /* wcstringutil.h */,
+				D0F5B46419CFCDE80090665E /* wcstringutil.h */,
-                                D0F5B46319CFCDE80090665E /* wcstringutil.cpp */,
+				D0F5B46319CFCDE80090665E /* wcstringutil.cpp */,
 				D0A0852713B3ACEE0099B651 /* wgetopt.h */,
 				D0A0855F13B3ACEE0099B651 /* wgetopt.cpp */,
 				D0A0852813B3ACEE0099B651 /* wildcard.h */,
@@ -926,6 +926,8 @@
 				"$(SRCROOT)/doc_src/umask.txt",
 				"$(SRCROOT)/doc_src/vared.txt",
 				"$(SRCROOT)/doc_src/while.txt",
+				"$(SRCROOT)/doc_src/true.txt",
+				"$(SRCROOT)/doc_src/false.txt",
 			);
 			outputPaths = (
 				"$(BUILT_PRODUCTS_DIR)/man/man1/alias.1",
@@ -998,6 +1000,8 @@
 				"$(BUILT_PRODUCTS_DIR)/man/man1/umask.1",
 				"$(BUILT_PRODUCTS_DIR)/man/man1/vared.1",
 				"$(BUILT_PRODUCTS_DIR)/man/man1/while.1",
+				"$(BUILT_PRODUCTS_DIR)/man/man1/true.1",
+				"$(BUILT_PRODUCTS_DIR)/man/man1/false.1",
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 			shellPath = /bin/sh;
@@ -1041,7 +1045,7 @@
 				D007692E1990137800CA4627 /* reader.cpp in Sources */,
 				D007692F1990137800CA4627 /* sanity.cpp in Sources */,
 				D00769301990137800CA4627 /* tokenizer.cpp in Sources */,
-                                D0F5B46619CFCEBC0090665E /* wcstringutil.cpp in Sources */,
+				D0F5B46619CFCEBC0090665E /* wcstringutil.cpp in Sources */,
 				D00769311990137800CA4627 /* wildcard.cpp in Sources */,
 				D00769321990137800CA4627 /* wgetopt.cpp in Sources */,
 				D00769331990137800CA4627 /* wutil.cpp in Sources */,
@@ -1094,7 +1098,7 @@
 				D0D02A67159837AD008E62BD /* complete.cpp in Sources */,
 				D0D02A69159837B2008E62BD /* env.cpp in Sources */,
 				D0D02A6A1598381A008E62BD /* exec.cpp in Sources */,
-                                D0F5B46519CFCDE80090665E /* wcstringutil.cpp in Sources */,
+				D0F5B46519CFCDE80090665E /* wcstringutil.cpp in Sources */,
 				D0D02A6B1598381F008E62BD /* expand.cpp in Sources */,
 				D00F63F119137E9D00FCCDEC /* fish_version.cpp in Sources */,
 				D0D02A6C15983829008E62BD /* highlight.cpp in Sources */,