git-gui: Make git-gui lib dir configurable at runime

Introduce the GIT_GUI_LIB_DIR environment variable, to tell git-gui
where to look for TCL libs.  This allows a git-gui which has been
built with a prefix of /foo to be run out of directory /bar.  This is
the equivalent of GIT_EXEC_PATH or GITPERLLIB but for git-gui's TCL
libraries.

Signed-off-by: David Turner <dturner@twitter.com>
Signed-off-by: Pat Thoyts <patthoyts@users.sourceforge.net>

Makefile

@@ -177,7 +177,8 @@ git-gui: GIT-VERSION-FILE GIT-GUI-VARS
 	echo then >>$@+ && \
 	echo '	'echo \'git-gui version '$(GITGUI_VERSION)'\' >>$@+ && \
 	echo else >>$@+ && \
-	echo '	'exec \''$(libdir_SQ)/Git Gui.app/Contents/MacOS/$(subst \,,$(TKEXECUTABLE))'\' \
+	echo '	libdir="$${GIT_GUI_LIB_DIR:-$(libdir_SQ)}"' >>$@+ && \
+	echo '	'exec \"'$$libdir/Git Gui.app/Contents/MacOS/$(subst \,,$(TKEXECUTABLE))'\" \
 		'"$$0" "$$@"' >>$@+ && \
 	echo fi >>$@+ && \
 	chmod +x $@+ && \

git-gui.sh

@@ -49,7 +49,11 @@ catch {rename send {}} ; # What an evil concept...
 ##
 ## locate our library
 
-set oguilib {@@GITGUI_LIBDIR@@}
+if { [info exists ::env(GIT_GUI_LIB_DIR) ] } {
+	set oguilib $::env(GIT_GUI_LIB_DIR)
+} else {
+	set oguilib {@@GITGUI_LIBDIR@@}
+}
 set oguirel {@@GITGUI_RELATIVE@@}
 if {$oguirel eq {1}} {
 	set oguilib [file dirname [file normalize $argv0]]

macosx/AppMain.tcl

@@ -1,5 +1,10 @@
 set gitexecdir {@@gitexecdir@@}
-set gitguilib  {@@GITGUI_LIBDIR@@}
+if { [info exists ::env(GIT_GUI_LIB_DIR) ] } {
+	set gitguilib $::env(GIT_GUI_LIB_DIR)
+} else {
+	set gitguilib {@@GITGUI_LIBDIR@@}
+}
+
 set env(PATH) "$gitexecdir:$env(PATH)"
 
 if {[string first -psn [lindex $argv 0]] == 0} {