git: Update to 2.51.0 (#5575)

git-2.43.0-git-gui.patch: refresh

the two remote scripts were dropped upstream with
https://github.com/git/git/commit/9a5e587d47c8d973d3484

git/git-2.43.0-git-gui.patch

@@ -1,7 +1,7 @@
---- git-2.43.0/git-gui/git-gui.sh.orig	2023-11-20 02:28:15.000000000 +0100
-+++ git-2.43.0/git-gui/git-gui.sh	2023-11-21 19:47:37.244720600 +0100
-@@ -75,6 +75,11 @@
- 	return $_iscygwin
+--- git-2.51.0/git-gui/git-gui.sh.orig	2025-08-18 02:18:23.000000000 +0200
++++ git-2.51.0/git-gui/git-gui.sh	2025-08-18 21:04:23.387867700 +0200
+@@ -93,6 +93,11 @@
+ 	}
  }
  
 +proc is_CygwinGit {} {
@@ -11,8 +11,8 @@
 +
  ######################################################################
  ##
- ## PATH lookup
-@@ -177,7 +182,11 @@
+ ## PATH lookup. Sanitize $PATH, assure exec/open use only that
+@@ -268,7 +273,11 @@
  if { [info exists ::env(GIT_GUI_LIB_DIR) ] } {
  	set oguilib $::env(GIT_GUI_LIB_DIR)
  } else {
@@ -25,20 +25,20 @@
  }
  set oguirel {@@GITGUI_RELATIVE@@}
  if {$oguirel eq {1}} {
-@@ -1285,7 +1294,11 @@
+@@ -1183,7 +1192,11 @@
+ load_config 0
+ apply_config
  
- # v1.7.0 introduced --show-toplevel to return the canonical work-tree
- if {[package vcompare $_git_version 1.7.0] >= 0} {
--	set _gitworktree [git rev-parse --show-toplevel]
-+	if {[is_Windows] && [is_CygwinGit]} {
-+		set _gitworktree [exec cygpath --windows [git rev-parse --show-toplevel]]
-+	} else {
-+		set _gitworktree [git rev-parse --show-toplevel]
-+	}
- } else {
- 	# try to set work tree from environment, core.worktree or use
- 	# cdup to obtain a relative path to the top of the worktree. If
-@@ -2254,7 +2267,11 @@
+-set _gitworktree [git rev-parse --show-toplevel]
++if {[is_Windows] && [is_CygwinGit]} {
++	set _gitworktree [exec cygpath --windows [git rev-parse --show-toplevel]]
++} else {
++	set _gitworktree [git rev-parse --show-toplevel]
++}
+ 
+ if {$_prefix ne {}} {
+ 	if {$_gitworktree eq {}} {
+@@ -2123,7 +2136,11 @@
  	if {[is_Cygwin]} {
  		set explorer "/bin/cygstart.exe --explore"
  	} elseif {[is_Windows]} {