diff --git a/git-gui/Makefile b/git-gui/Makefile
index 27bbe051de..69b0b84435 100644
--- a/git-gui/Makefile
+++ b/git-gui/Makefile
@@ -186,6 +186,7 @@ install: all
 	$(QUIET)$(INSTALL_D0)'$(DESTDIR_SQ)$(gitexecdir_SQ)' $(INSTALL_D1)
 	$(QUIET)$(INSTALL_X0)git-gui $(INSTALL_X1) '$(DESTDIR_SQ)$(gitexecdir_SQ)'
 	$(QUIET)$(INSTALL_X0)git-gui--askpass $(INSTALL_X1) '$(DESTDIR_SQ)$(gitexecdir_SQ)'
+	$(QUIET)$(INSTALL_X0)git-gui--askyesno $(INSTALL_X1) '$(DESTDIR_SQ)$(gitexecdir_SQ)'
 	$(QUIET)$(foreach p,$(GITGUI_BUILT_INS), $(INSTALL_L0)'$(DESTDIR_SQ)$(gitexecdir_SQ)/$p' $(INSTALL_L1)'$(DESTDIR_SQ)$(gitexecdir_SQ)/git-gui' $(INSTALL_L2)'$(DESTDIR_SQ)$(gitexecdir_SQ)/$p' $(INSTALL_L3) &&) true
 ifdef GITGUI_WINDOWS_WRAPPER
 	$(QUIET)$(INSTALL_R0)git-gui.tcl $(INSTALL_R1) '$(DESTDIR_SQ)$(gitexecdir_SQ)'
@@ -200,6 +201,7 @@ uninstall:
 	$(QUIET)$(CLEAN_DST) '$(DESTDIR_SQ)$(gitexecdir_SQ)'
 	$(QUIET)$(REMOVE_F0)'$(DESTDIR_SQ)$(gitexecdir_SQ)'/git-gui $(REMOVE_F1)
 	$(QUIET)$(REMOVE_F0)'$(DESTDIR_SQ)$(gitexecdir_SQ)'/git-gui--askpass $(REMOVE_F1)
+	$(QUIET)$(REMOVE_F0)'$(DESTDIR_SQ)$(gitexecdir_SQ)'/git-gui--askyesno $(REMOVE_F1)
 	$(QUIET)$(foreach p,$(GITGUI_BUILT_INS), $(REMOVE_F0)'$(DESTDIR_SQ)$(gitexecdir_SQ)'/$p $(REMOVE_F1) &&) true
 ifdef GITGUI_WINDOWS_WRAPPER
 	$(QUIET)$(REMOVE_F0)'$(DESTDIR_SQ)$(gitexecdir_SQ)'/git-gui.tcl $(REMOVE_F1)
diff --git a/git-gui/git-gui--askyesno b/git-gui/git-gui--askyesno
new file mode 100755
index 0000000000..142d1bc3de
--- /dev/null
+++ b/git-gui/git-gui--askyesno
@@ -0,0 +1,63 @@
+#!/bin/sh
+# Tcl ignores the next line -*- tcl -*- \
+exec wish "$0" -- "$@"
+
+# This is an implementation of a simple yes no dialog
+# which is injected into the git commandline by git gui
+# in case a yesno question needs to be answered.
+#
+# The window title, which defaults to "Question?", can be
+# overridden via the optional `--title` command-line
+# option.
+
+set NS {}
+set use_ttk [package vsatisfies [package provide Tk] 8.5]
+if {$use_ttk} {
+	set NS ttk
+}
+
+set title "Question?"
+if {$argc < 1} {
+	puts stderr "Usage: $argv0 <question>"
+	exit 1
+} else {
+	if {$argc > 2 && [lindex $argv 0] == "--title"} {
+		set title [lindex $argv 1]
+		set argv [lreplace $argv 0 1]
+	}
+	set prompt [join $argv " "]
+}
+
+${NS}::frame .t
+${NS}::label .t.m -text $prompt -justify center -width 40
+.t.m configure -wraplength 400
+pack .t.m -side top -fill x -padx 20 -pady 20 -expand 1
+pack .t -side top -fill x -ipadx 20 -ipady 20 -expand 1
+
+${NS}::frame .b
+${NS}::frame .b.left -width 200
+${NS}::button .b.yes -text Yes -command {exit 0}
+${NS}::button .b.no  -text No  -command {exit 1}
+
+pack .b.left -side left -expand 1 -fill x
+pack .b.yes -side left -expand 1
+pack .b.no -side right -expand 1 -ipadx 5
+pack .b -side bottom -fill x -ipadx 20 -ipady 15
+
+bind . <Key-Return> {exit 0}
+bind . <Key-Escape> {exit 1}
+
+if {$::tcl_platform(platform) eq {windows}} {
+	set icopath [file dirname [file normalize $argv0]]
+	if {[file tail $icopath] eq {git-core}} {
+		set icopath [file dirname $icopath]
+	}
+	set icopath [file dirname $icopath]
+	set icopath [file join $icopath share git git-for-windows.ico]
+	if {[file exists $icopath]} {
+		wm iconbitmap . -default $icopath
+	}
+}
+
+wm title . $title
+tk::PlaceWindow .
diff --git a/git-gui/git-gui.sh b/git-gui/git-gui.sh
index a931d7f7c9..d3d3aa14a9 100755
--- a/git-gui/git-gui.sh
+++ b/git-gui/git-gui.sh
@@ -103,7 +103,6 @@ if {[is_Windows]} {
 	set _path_sep {:}
 }
 
-set _search_path {}
 set _path_seen [dict create]
 foreach p [split $env(PATH) $_path_sep] {
 	# Keep only absolute paths, getting rid of ., empty, etc.
@@ -112,12 +111,9 @@ foreach p [split $env(PATH) $_path_sep] {
 	}
 	# Keep only the first occurence of any duplicates.
 	set norm_p [file normalize $p]
-	if {[dict exists $_path_seen $norm_p]} {
-		continue
-	}
 	dict set _path_seen $norm_p 1
-	lappend _search_path $norm_p
 }
+set _search_path [dict keys $_path_seen]
 unset _path_seen
 
 set env(PATH) [join $_search_path $_path_sep]
@@ -583,21 +579,6 @@ proc open_cmd_pipe {cmd path} {
 	return [open |$run r]
 }
 
-proc _lappend_nice {cmd_var} {
-	global _nice
-	upvar $cmd_var cmd
-
-	if {![info exists _nice]} {
-		set _nice [_which nice]
-		if {[catch {safe_exec [list $_nice git version]}]} {
-			set _nice {}
-		}
-	}
-	if {$_nice ne {}} {
-		lappend cmd $_nice
-	}
-}
-
 proc git {args} {
 	git_redir $args {}
 }
@@ -631,15 +612,14 @@ proc git_read {cmd {redir {}}} {
 	return [safe_open_command $cmdp $redir]
 }
 
+set _nice [list [_which nice]]
+if {[catch {safe_exec [list {*}$_nice git version]}]} {
+	set _nice {}
+}
+
 proc git_read_nice {cmd} {
-	global _git
-	set opt [list]
-
-	_lappend_nice opt
-
-	set cmdp [concat [list $_git] $cmd]
-
-	return [safe_open_command [concat $opt $cmdp]]
+	set cmdp [list {*}$::_nice $::_git {*}$cmd]
+	return [safe_open_command $cmdp]
 }
 
 proc git_write {cmd} {
@@ -1130,6 +1110,12 @@ set argv0dir [file dirname [file normalize $::argv0]]
 if {![info exists env(SSH_ASKPASS)]} {
 	set env(SSH_ASKPASS) [file join $argv0dir git-gui--askpass]
 }
+if {![info exists env(GIT_ASKPASS)]} {
+	set env(GIT_ASKPASS) [file join $argv0dir git-gui--askpass]
+}
+if {![info exists env(GIT_ASK_YESNO)]} {
+	set env(GIT_ASK_YESNO) [file join $argv0dir git-gui--askyesno]
+}
 unset argv0dir
 
 ######################################################################
diff --git a/git-gui/lib/index.tcl b/git-gui/lib/index.tcl
index 7aa09c7728..e1d38e54be 100644
--- a/git-gui/lib/index.tcl
+++ b/git-gui/lib/index.tcl
@@ -425,6 +425,11 @@ proc revert_helper {txt paths} {
 
 	if {![lock_index begin-update]} return
 
+	# Workaround for Tcl < 9.0: chord namespaces are not obeyed and
+	# operated in the global namespace. This clears an error that could
+	# have been left over from a previous operation.
+	set ::err {}
+
 	# Common "after" functionality that waits until multiple asynchronous
 	# operations are complete (by waiting for them to activate their notes
 	# on the chord).
@@ -432,7 +437,7 @@ proc revert_helper {txt paths} {
 	# The asynchronous operations are each indicated below by a comment
 	# before the code block that starts the async operation.
 	set after_chord [SimpleChord::new {
-		if {[string trim $err] != ""} {
+		if {[info exists err] && [string trim $err] ne ""} {
 			rescan_on_error $err
 		} else {
 			unlock_index