Revert "git-gui: set GIT_DIR and GIT_WORK_TREE after setup"

This reverts commit a9fa11f.

Author: hvoigt

git-gui/git-gui.sh

@@ -1340,9 +1340,6 @@ if {[lindex $_reponame end] eq {.git}} {
 	set _reponame [lindex $_reponame end]
 }
 
-set env(GIT_DIR) $_gitdir
-set env(GIT_WORK_TREE) $_gitworktree
-
 ######################################################################
 ##
 ## global init
@@ -2165,7 +2162,7 @@ set starting_gitk_msg [mc "Starting gitk... please wait..."]
 
 proc do_gitk {revs {is_submodule false}} {
 	global current_diff_path file_states current_diff_side ui_index
-	global _gitdir _gitworktree
+	global _gitworktree
 
 	# -- Always start gitk through whatever we were loaded with.  This
 	#    lets us bypass using shell process on Windows systems.
@@ -2177,12 +2174,19 @@ proc do_gitk {revs {is_submodule false}} {
 	} else {
 		global env
 
+		if {[info exists env(GIT_DIR)]} {
+			set old_GIT_DIR $env(GIT_DIR)
+		} else {
+			set old_GIT_DIR {}
+		}
+
 		set pwd [pwd]
 
 		if {!$is_submodule} {
 			if {![is_bare]} {
 				cd $_gitworktree
 			}
+			set env(GIT_DIR) [file normalize [gitdir]]
 		} else {
 			cd $current_diff_path
 			if {$revs eq {--}} {
@@ -2203,18 +2207,15 @@ proc do_gitk {revs {is_submodule false}} {
 				}
 				set revs $old_sha1...$new_sha1
 			}
-			# GIT_DIR and GIT_WORK_TREE for the submodule are not the ones
-			# we've been using for the main repository, so unset them.
-			# TODO we could make life easier (start up faster?) for gitk
-			# by setting these to the appropriate values to allow gitk
-			# to skip the heuristics to find their proper value
-			unset env(GIT_DIR)
-			unset env(GIT_WORK_TREE)
+			if {[info exists env(GIT_DIR)]} {
+				unset env(GIT_DIR)
+			}
 		}
 		eval exec $cmd $revs "--" "--" &
 
-		set env(GIT_DIR) $_gitdir
-		set env(GIT_WORK_TREE) $_gitworktree
+		if {$old_GIT_DIR ne {}} {
+			set env(GIT_DIR) $old_GIT_DIR
+		}
 		cd $pwd
 
 		ui_status $::starting_gitk_msg
@@ -2235,20 +2236,22 @@ proc do_git_gui {} {
 		error_popup [mc "Couldn't find git gui in PATH"]
 	} else {
 		global env
-		global _gitdir _gitworktree
 
-		# see note in do_gitk about unsetting these vars when
-		# running tools in a submodule
-		unset env(GIT_DIR)
-		unset env(GIT_WORK_TREE)
+		if {[info exists env(GIT_DIR)]} {
+			set old_GIT_DIR $env(GIT_DIR)
+			unset env(GIT_DIR)
+		} else {
+			set old_GIT_DIR {}
+		}
 
 		set pwd [pwd]
 		cd $current_diff_path
 
 		eval exec $exe gui &
 
-		set env(GIT_DIR) $_gitdir
-		set env(GIT_WORK_TREE) $_gitworktree
+		if {$old_GIT_DIR ne {}} {
+			set env(GIT_DIR) $old_GIT_DIR
+		}
 		cd $pwd
 
 		ui_status $::starting_gitk_msg