diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 4fff34487453d9..f9085773f47de4 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -413,9 +413,9 @@ jobs:
         # A RHEL 8 compatible distro.  Supported until 2029-05-31.
         - jobname: almalinux-8
           image: almalinux:8
-        # Supported until 2026-08-31.
-        - jobname: debian-11
-          image: debian:11
+        # Supported until 2028-06-30.
+        - jobname: debian-12
+          image: debian:12
     env:
       jobname: ${{matrix.vector.jobname}}
       CC: ${{matrix.vector.cc}}
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 0242283c3c5571..cd6fd4a5047e87 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -71,9 +71,9 @@ test:linux:
       # A RHEL 8 compatible distro.  Supported until 2029-05-31.
       - jobname: almalinux-8
         image: almalinux:8
-      # Supported until 2026-08-31.
-      - jobname: debian-11
-        image: debian:11
+      # Supported until 2028-06-30.
+      - jobname: debian-12
+        image: debian:12
   artifacts:
     paths:
       - t/failed-test-artifacts
diff --git a/Documentation/RelNotes/2.56.0.adoc b/Documentation/RelNotes/2.56.0.adoc
index c72c2ddac6ff86..28f555da03abf7 100644
--- a/Documentation/RelNotes/2.56.0.adoc
+++ b/Documentation/RelNotes/2.56.0.adoc
@@ -512,6 +512,12 @@ Performance, Internal Implementation, Development Support etc.
    during a concurrent geometric repack, and 'git replay' has been
    fixed to not segfault when reading such missing objects.
 
+ * A collection of patches from Git for Windows has been upstreamed,
+   mostly focusing on simplifying and robustifying build configurations
+   for MinGW/MSYS2, dropping obsolete compatibility options, and allowing
+   the main 'git.exe' to be used directly without the extra wrapper
+   process on Windows.
+
 
 Fixes since v2.55
 -----------------
@@ -804,6 +810,17 @@ Fixes since v2.55
    trailing slashes.
    (merge 2e8a9d94b0 rs/worktree-add-basename-fixes later to maint).
 
+ * The CI job for Debian 11 has been updated to use Debian 12, as the
+   former is now out of the LTS period.
+   (merge 00fa850235 jk/ci-bump-debian-to-12 later to maint).
+
+ * The CI script to install dependencies for the documentation build
+   has been updated to install asciidoctor directly via the system
+   package manager instead of pinning to an older version via gem.
+   Additionally, an obsolete variable used for retired Azure Pipelines
+   environments has been removed.
+   (merge 1c1eed13bd jk/ci-use-system-asciidoctor later to maint).
+
  * Other code cleanup, docfix, build fix, etc.
    (merge 026636128f ss/submittingpatches-typofix later to maint).
    (merge d2af22cc21 jc/rerere-doc-typofix later to maint).
diff --git a/ci/install-dependencies.sh b/ci/install-dependencies.sh
index 10c3530d1aacdd..2f61fbb07c577d 100755
--- a/ci/install-dependencies.sh
+++ b/ci/install-dependencies.sh
@@ -164,9 +164,8 @@ sparse)
 		libexpat-dev gettext zlib1g-dev sparse
 	;;
 Documentation)
-	sudo apt-get -q -y install asciidoc xmlto docbook-xsl-ns make
+	sudo apt-get -q -y install asciidoc xmlto docbook-xsl-ns make ruby
 
-	test -n "$ALREADY_HAVE_ASCIIDOCTOR" ||
 	sudo gem install --version 1.5.8 asciidoctor
 	sudo gem install concurrent-ruby
 	;;
diff --git a/compat/mingw.c b/compat/mingw.c
index 4c2f26d4548147..0c8179f3458bb8 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -3157,6 +3157,45 @@ int xwcstoutf(char *utf, const wchar_t *wcs, size_t utflen)
 	return -1;
 }
 
+#ifdef ENSURE_MSYSTEM_IS_SET
+#if !defined(RUNTIME_PREFIX) || !defined(HAVE_WPGMPTR) || !defined(MINGW_PREFIX)
+static size_t append_system_bin_dirs(char *path UNUSED, size_t size UNUSED)
+{
+	return 0;
+}
+#else
+static size_t append_system_bin_dirs(char *path, size_t size)
+{
+	char prefix[32768];
+	const char *slash;
+	size_t len = xwcstoutf(prefix, _wpgmptr, sizeof(prefix)), off = 0;
+
+	if (len == 0 || len >= sizeof(prefix) ||
+	    !(slash = find_last_dir_sep(prefix)))
+		return 0;
+	/* strip trailing `git.exe` */
+	len = slash - prefix;
+
+	/* strip trailing `cmd` or `<mingw-prefix>\bin` or `bin` or `libexec\git-core` */
+	if (strip_suffix_mem(prefix, &len, "\\" MINGW_PREFIX "\\libexec\\git-core") ||
+	    strip_suffix_mem(prefix, &len, "\\" MINGW_PREFIX "\\bin"))
+		off += xsnprintf(path + off, size - off,
+				 "%.*s\\" MINGW_PREFIX "\\bin;", (int)len, prefix);
+	else if (strip_suffix_mem(prefix, &len, "\\cmd") ||
+		 strip_suffix_mem(prefix, &len, "\\bin") ||
+		 strip_suffix_mem(prefix, &len, "\\libexec\\git-core"))
+		off += xsnprintf(path + off, size - off,
+				 "%.*s\\" MINGW_PREFIX "\\bin;", (int)len, prefix);
+	else
+		return 0;
+
+	off += xsnprintf(path + off, size - off,
+			 "%.*s\\usr\\bin;", (int)len, prefix);
+	return off;
+}
+#endif
+#endif
+
 static void setup_windows_environment(void)
 {
 	char *tmp = getenv("TMPDIR");
@@ -3208,6 +3247,35 @@ static void setup_windows_environment(void)
 		if (!tmp && (tmp = getenv("USERPROFILE")))
 			setenv("HOME", tmp, 1);
 	}
+
+	if (!getenv("PLINK_PROTOCOL"))
+		setenv("PLINK_PROTOCOL", "ssh", 0);
+
+#ifdef ENSURE_MSYSTEM_IS_SET
+	if (!(tmp = getenv("MSYSTEM")) || !tmp[0]) {
+		const char *home = getenv("HOME"), *path = getenv("PATH");
+		char buf[32768];
+		size_t off = 0;
+
+		setenv("MSYSTEM", ENSURE_MSYSTEM_IS_SET, 1);
+
+		if (home)
+			off += xsnprintf(buf + off, sizeof(buf) - off,
+					 "%s\\bin;", home);
+		off += append_system_bin_dirs(buf + off, sizeof(buf) - off);
+		if (path)
+			off += xsnprintf(buf + off, sizeof(buf) - off,
+					 "%s", path);
+		else if (off > 0)
+			buf[off - 1] = '\0';
+		else
+			buf[0] = '\0';
+		setenv("PATH", buf, 1);
+	}
+#endif
+
+	if (!getenv("LC_ALL") && !getenv("LC_CTYPE") && !getenv("LANG"))
+		setenv("LC_CTYPE", "C.UTF-8", 1);
 }
 
 int mingw_platform_has_symlinks(void)
diff --git a/config.mak.uname b/config.mak.uname
index 95ef6e64dcabff..e28870434d9232 100644
--- a/config.mak.uname
+++ b/config.mak.uname
@@ -465,14 +465,8 @@ ifeq ($(uname_S),Windows)
 	GIT_VERSION := $(GIT_VERSION).MSVC
 	pathsep = ;
 	# Assume that this is built in Git for Windows' SDK
-        ifeq (MINGW32,$(MSYSTEM))
-		prefix = /mingw32
-        else
-                ifeq (CLANGARM64,$(MSYSTEM))
-			prefix = /clangarm64
-                else
-			prefix = /mingw64
-                endif
+        ifneq (,$(MSYSTEM))
+		prefix = $(MINGW_PREFIX)
         endif
 	# Prepend MSVC 64-bit tool-chain to PATH.
 	#
@@ -525,7 +519,8 @@ ifeq ($(uname_S),Windows)
 	NO_POSIX_GOODIES = UnfortunatelyYes
 	NATIVE_CRLF = YesPlease
 	DEFAULT_HELP_FORMAT = html
-ifeq (/mingw64,$(subst 32,64,$(subst clangarm,mingw,$(prefix))))
+	SKIP_DASHED_BUILT_INS = YabbaDabbaDoo
+ifneq (,$(MINGW_PREFIX))
 	# Move system config into top-level /etc/
 	ETC_GITCONFIG = ../etc/gitconfig
 	ETC_GITATTRIBUTES = ../etc/gitattributes
@@ -541,7 +536,9 @@ endif
 		compat/win32/pthread.o compat/win32/syslog.o \
 		compat/win32/trace2_win32_process_info.o \
 		compat/win32/dirent.o
-	COMPAT_CFLAGS = -D__USE_MINGW_ACCESS -DDETECT_MSYS_TTY -DNOGDI -DHAVE_STRING_H -Icompat -Icompat/regex -Icompat/win32 -DSTRIP_EXTENSION=\".exe\"
+	COMPAT_CFLAGS = -D__USE_MINGW_ACCESS -DDETECT_MSYS_TTY \
+		-DENSURE_MSYSTEM_IS_SET="\"$(MSYSTEM)\"" -DMINGW_PREFIX="\"$(patsubst /%,%,$(MINGW_PREFIX))\"" \
+		-DNOGDI -DHAVE_STRING_H -Icompat -Icompat/regex -Icompat/win32 -DSTRIP_EXTENSION=\".exe\"
 	BASIC_LDFLAGS = -IGNORE:4217 -IGNORE:4049 -NOLOGO -ENTRY:wmainCRTStartup -SUBSYSTEM:CONSOLE
 	# invalidcontinue.obj allows Git's source code to close the same file
 	# handle twice, or to access the osfhandle of an already-closed stdout
@@ -718,6 +715,7 @@ ifeq ($(uname_S),MINGW)
 	FSMONITOR_DAEMON_BACKEND = win32
 	FSMONITOR_OS_SETTINGS = win32
 
+	SKIP_DASHED_BUILT_INS = YabbaDabbaDoo
 	RUNTIME_PREFIX = YesPlease
 	HAVE_WPGMPTR = YesWeDo
 	NO_ST_BLOCKS_IN_STRUCT_STAT = YesPlease
@@ -756,26 +754,25 @@ ifeq ($(uname_S),MINGW)
         ifneq (,$(findstring -O,$(filter-out -O0 -Og,$(CFLAGS))))
 		BASIC_LDFLAGS += -Wl,--dynamicbase
         endif
-        ifeq (MINGW32,$(MSYSTEM))
-		prefix = /mingw32
-		HOST_CPU = i686
-		BASIC_LDFLAGS += -Wl,--pic-executable,-e,_mainCRTStartup
-        endif
-        ifeq (MINGW64,$(MSYSTEM))
-		prefix = /mingw64
-		HOST_CPU = x86_64
-		BASIC_LDFLAGS += -Wl,--pic-executable,-e,mainCRTStartup
-        else ifeq (CLANGARM64,$(MSYSTEM))
-		prefix = /clangarm64
-		HOST_CPU = aarch64
-		BASIC_LDFLAGS += -Wl,--pic-executable,-e,mainCRTStartup
-        else
-		COMPAT_CFLAGS += -D_USE_32BIT_TIME_T
-		BASIC_LDFLAGS += -Wl,--large-address-aware
+        ifneq (,$(MSYSTEM))
+                ifeq ($(MINGW_PREFIX),$(filter-out /%,$(MINGW_PREFIX)))
+			# Override if empty or does not start with a slash
+			MINGW_PREFIX := /$(shell echo '$(MSYSTEM)' | tr A-Z a-z)
+                endif
+		prefix = $(MINGW_PREFIX)
+		HOST_CPU = $(patsubst %-w64-mingw32,%,$(MINGW_CHOST))
+		BASIC_LDFLAGS += -Wl,--pic-executable
+		COMPAT_CFLAGS += -DDETECT_MSYS_TTY \
+			-DENSURE_MSYSTEM_IS_SET="\"$(MSYSTEM)\"" \
+			-DMINGW_PREFIX="\"$(patsubst /%,%,$(MINGW_PREFIX))\""
+                ifeq (MINGW32,$(MSYSTEM))
+			BASIC_LDFLAGS += -Wl,--large-address-aware
+                endif
+		# Move system config into top-level /etc/
+		ETC_GITCONFIG = ../etc/gitconfig
+		ETC_GITATTRIBUTES = ../etc/gitattributes
         endif
-	CC = gcc
-	COMPAT_CFLAGS += -D__USE_MINGW_ANSI_STDIO=0 -DDETECT_MSYS_TTY \
-		-fstack-protector-strong
+	COMPAT_CFLAGS += -D__USE_MINGW_ANSI_STDIO=0 -fstack-protector-strong
 	EXTLIBS += -lntdll
 	EXTRA_PROGRAMS += headless-git$X
 	INSTALL = /bin/install
@@ -783,11 +780,7 @@ ifeq ($(uname_S),MINGW)
 	HAVE_LIBCHARSET_H = YesPlease
 	USE_GETTEXT_SCHEME = fallthrough
 	USE_LIBPCRE = YesPlease
-        ifeq (/mingw64,$(subst 32,64,$(subst clangarm,mingw,$(prefix))))
-		# Move system config into top-level /etc/
-		ETC_GITCONFIG = ../etc/gitconfig
-		ETC_GITATTRIBUTES = ../etc/gitattributes
-        endif
+	NO_PYTHON =
 endif
 ifeq ($(uname_S),QNX)
 	COMPAT_CFLAGS += -DSA_RESTART=0
diff --git a/contrib/buildsystems/CMakeLists.txt b/contrib/buildsystems/CMakeLists.txt
index 8f56203f34d9bc..e76bd19b65642b 100644
--- a/contrib/buildsystems/CMakeLists.txt
+++ b/contrib/buildsystems/CMakeLists.txt
@@ -256,7 +256,14 @@ if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
 				_CONSOLE DETECT_MSYS_TTY STRIP_EXTENSION=".exe"  NO_SYMLINK_HEAD UNRELIABLE_FSTAT
 				NOGDI OBJECT_CREATION_MODE=1 __USE_MINGW_ANSI_STDIO=0
 				OVERRIDE_STRDUP MMAP_PREVENTS_DELETE USE_WIN32_MMAP
-				HAVE_WPGMPTR ENSURE_MSYSTEM_IS_SET HAVE_RTLGENRANDOM)
+				HAVE_WPGMPTR HAVE_RTLGENRANDOM)
+	if(CMAKE_GENERATOR_PLATFORM STREQUAL "x64")
+		add_compile_definitions(ENSURE_MSYSTEM_IS_SET="MINGW64" MINGW_PREFIX="mingw64")
+	elseif(CMAKE_GENERATOR_PLATFORM STREQUAL "arm64")
+		add_compile_definitions(ENSURE_MSYSTEM_IS_SET="CLANGARM64" MINGW_PREFIX="clangarm64")
+	elseif(CMAKE_GENERATOR_PLATFORM STREQUAL "x86")
+		add_compile_definitions(ENSURE_MSYSTEM_IS_SET="MINGW32" MINGW_PREFIX="mingw32")
+	endif()
 	list(APPEND compat_SOURCES
 		compat/mingw.c
 		compat/winansi.c
diff --git a/gitk-git/README.md b/gitk-git/README.md
index 2e307463c61d63..c4027882aeba19 100644
--- a/gitk-git/README.md
+++ b/gitk-git/README.md
@@ -79,13 +79,14 @@ are also accepted.
 All commits must be signed off (use `git commit --signoff`) and should
 have commit messages prefixed with `gitk:`.
 
-Email Patches
--------------
-
 Send patches to git@vger.kernel.org and CC j6t@kdbg.org. See the Git
 project's [patch submission guidelines](https://git-scm.com/docs/SubmittingPatches)
 for detailed instructions on creating and sending patches.
 
+Please do not submit work that originated from AI, because this project
+is down-streamed to the Git project, which has a rather
+[strict AI guideline](https://git-scm.com/docs/SubmittingPatches#ai).
+
 License
 =======
 
diff --git a/gitk-git/gitk b/gitk-git/gitk
index 0f3571050bef1c..9506739c503b1a 100755
--- a/gitk-git/gitk
+++ b/gitk-git/gitk
@@ -11801,8 +11801,6 @@ proc prefspage_general {notebook} {
 }
 
 proc prefspage_colors {notebook} {
-    global bgcolor fgcolor ctext diffcolors selectbgcolor markbgcolor
-    global diffbgcolors linkfgcolor
     global themeloader
 
     set page [create_prefs_page $notebook.colors]
@@ -11834,75 +11832,72 @@ proc prefspage_colors {notebook} {
 
     ttk::label $page.cdisp -text [mc "Colors: press to choose"] -font mainfontbold
     grid $page.cdisp - -sticky w -pady 10
-    label $page.bg -padx 40 -relief sunk -background $bgcolor
-    ttk::button $page.bgbut -text [mc "Background"] \
-        -command [list choosecolor bgcolor {} $page [mc "background"]]
-    grid x $page.bgbut $page.bg -sticky w
-
-    label $page.fg -padx 40 -relief sunk -background $fgcolor
-    ttk::button $page.fgbut -text [mc "Foreground"] \
-        -command [list choosecolor fgcolor {} $page [mc "foreground"]]
-    grid x $page.fgbut $page.fg -sticky w
-
-    label $page.diffold -padx 40 -relief sunk -background [lindex $diffcolors 0]
-    ttk::button $page.diffoldbut -text [mc "Diff: old lines"] \
-        -command [list choosecolor diffcolors 0 $page [mc "diff old lines"]]
-    grid x $page.diffoldbut $page.diffold -sticky w
-
-    label $page.diffoldbg -padx 40 -relief sunk -background [lindex $diffbgcolors 0]
-    ttk::button $page.diffoldbgbut -text [mc "Diff: old lines bg"] \
-        -command [list choosecolor diffbgcolors 0 $page [mc "diff old lines bg"]]
-    grid x $page.diffoldbgbut $page.diffoldbg -sticky w
-
-    label $page.diffnew -padx 40 -relief sunk -background [lindex $diffcolors 1]
-    ttk::button $page.diffnewbut -text [mc "Diff: new lines"] \
-        -command [list choosecolor diffcolors 1 $page [mc "diff new lines"]]
-    grid x $page.diffnewbut $page.diffnew -sticky w
-
-    label $page.diffnewbg -padx 40 -relief sunk -background [lindex $diffbgcolors 1]
-    ttk::button $page.diffnewbgbut -text [mc "Diff: new lines bg"] \
-        -command [list choosecolor diffbgcolors 1 $page [mc "diff new lines bg"]]
-    grid x $page.diffnewbgbut $page.diffnewbg -sticky w
-
-    label $page.hunksep -padx 40 -relief sunk -background [lindex $diffcolors 2]
-    ttk::button $page.hunksepbut -text [mc "Diff: hunk header"] \
-        -command [list choosecolor diffcolors 2 $page [mc "diff hunk header"]]
-    grid x $page.hunksepbut $page.hunksep -sticky w
-
-    label $page.markbgsep -padx 40 -relief sunk -background $markbgcolor
-    ttk::button $page.markbgbut -text [mc "Marked line bg"] \
-        -command [list choosecolor markbgcolor {} $page [mc "marked line background"]]
-    grid x $page.markbgbut $page.markbgsep -sticky w
-
-    label $page.selbgsep -padx 40 -relief sunk -background $selectbgcolor
-    ttk::button $page.selbgbut -text [mc "Select bg"] \
-        -command [list choosecolor selectbgcolor {} $page [mc "background"]]
-    grid x $page.selbgbut $page.selbgsep -sticky w
-
-    label $page.linkfg -padx 40 -relief sunk -background $linkfgcolor
-    ttk::button $page.linkfgbut -text [mc "Link"] \
-        -command [list choosecolor linkfgcolor {} $page [mc "link"]]
-    grid x $page.linkfgbut $page.linkfg -sticky w
+
+    set coloruielems [list \
+        bg          bgcolor {} \
+                    [mc "Background"] \
+                    [mc "choose background color"] \
+        fg          fgcolor {} \
+                    [mc "Main text"] \
+                    [mc "choose main text color"] \
+        selbg       selectbgcolor {} \
+                    [mc "Selected text background"] \
+                    [mc "choose background color of selected text"] \
+        linkfg      linkfgcolor {} \
+                    [mc "Link text"] \
+                    [mc "choose color of link text"] \
+        diffold     diffcolors 0 \
+                    [mc "Old line text"] \
+                    [mc "choose text color of old lines"] \
+        diffoldbg   diffbgcolors 0 \
+                    [mc "Old line background"] \
+                    [mc "choose background color of old lines"] \
+        diffnew     diffcolors 1 \
+                    [mc "New line text"] \
+                    [mc "choose text color of new lines"] \
+        diffnewbg   diffbgcolors 1 \
+                    [mc "New line background"] \
+                    [mc "choose background color of new lines"] \
+        hunksep     diffcolors 2 \
+                    [mc "Hunk header text"] \
+                    [mc "choose text color of hunk headers"] \
+        markbg      markbgcolor {} \
+                    [mc "Marked line background"] \
+                    [mc "choose background color of marked lines"] \
+    ]
+
+    foreach {uielem colorvar idx label title} $coloruielems {
+        ttk::label $page.$uielem -text $label
+        button $page.${uielem}btn -padx 40 -pady 0 -borderwidth 2 \
+            -command [list choosecolor $colorvar $idx $page $title]
+        grid x $page.$uielem $page.${uielem}btn -sticky w -pady 1
+    }
 
     grid columnconfigure $page 2 -weight 1
+    prefspage_set_colorswatches $page
 
     return $page
 }
 
 proc prefspage_set_colorswatches {page} {
-    global bgcolor fgcolor ctext diffcolors selectbgcolor markbgcolor
+    global bgcolor fgcolor diffcolors selectbgcolor markbgcolor
     global diffbgcolors linkfgcolor
 
-    $page.bg configure -background $bgcolor
-    $page.fg configure -background $fgcolor
-    $page.diffold configure -background [lindex $diffcolors 0]
-    $page.diffoldbg configure -background [lindex $diffbgcolors 0]
-    $page.diffnew configure -background [lindex $diffcolors 1]
-    $page.diffnewbg configure -background [lindex $diffbgcolors 1]
-    $page.hunksep configure -background [lindex $diffcolors 2]
-    $page.markbgsep configure -background $markbgcolor
-    $page.selbgsep configure -background $selectbgcolor
-    $page.linkfg configure -background $linkfgcolor
+    set coloruielems [list \
+        bg        $bgcolor \
+        fg        $fgcolor \
+        diffold   [lindex $diffcolors 0] \
+        diffoldbg [lindex $diffbgcolors 0] \
+        diffnew   [lindex $diffcolors 1] \
+        diffnewbg [lindex $diffbgcolors 1] \
+        hunksep   [lindex $diffcolors 2] \
+        markbg    $markbgcolor \
+        selbg     $selectbgcolor \
+        linkfg    $linkfgcolor \
+    ]
+    foreach {uielem color} $coloruielems {
+        $page.${uielem}btn configure -background $color -activebackground $color
+    }
 }
 
 proc prefspage_fonts {notebook} {
@@ -12019,11 +12014,11 @@ proc choose_themeloader {prefspage} {
     }
 }
 
-proc choosecolor {v vi prefspage x} {
+proc choosecolor {v vi prefspage title} {
     global $v
 
     set c [tk_chooseColor -initialcolor [lindex [set $v] $vi] \
-               -title [mc "Gitk: choose color for %s" $x]]
+               -title "Gitk: $title"]
     if {$c eq {}} return
     lset $v $vi $c
     set_gui_colors
diff --git a/meson.build b/meson.build
index d86f2acd2b2a46..0a95d90d211fd6 100644
--- a/meson.build
+++ b/meson.build
@@ -1318,7 +1318,6 @@ elif host_machine.system() == 'windows'
 
   libgit_c_args += [
     '-DDETECT_MSYS_TTY',
-    '-DENSURE_MSYSTEM_IS_SET',
     '-DNATIVE_CRLF',
     '-DNOGDI',
     '-DNO_POSIX_GOODIES',
@@ -1328,6 +1327,20 @@ elif host_machine.system() == 'windows'
     '-D__USE_MINGW_ANSI_STDIO=0',
   ]
 
+  msystem = get_option('msystem')
+  if msystem != ''
+    mingw_prefix = get_option('mingw_prefix')
+    if mingw_prefix == ''
+      mingw_prefix = msystem.to_lower()
+    elif mingw_prefix.startswith('/')
+      mingw_prefix = mingw_prefix.substring(1)
+    endif
+    libgit_c_args += [
+      '-DENSURE_MSYSTEM_IS_SET="' + msystem + '"',
+      '-DMINGW_PREFIX="' + mingw_prefix + '"'
+    ]
+  endif
+
   libgit_dependencies += compiler.find_library('ntdll')
   libgit_include_directories += 'compat/win32'
   if compiler.get_id() == 'msvc'
diff --git a/meson_options.txt b/meson_options.txt
index dc88f130d754a1..becf4689bf63b1 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -21,6 +21,10 @@ option('runtime_prefix', type: 'boolean', value: false,
   description: 'Resolve ancillary tooling and support files relative to the location of the runtime binary instead of hard-coding them into the binary.')
 option('sane_tool_path', type: 'array', value: [],
   description: 'An array of paths to pick up tools from in case the normal tools are broken or lacking.')
+option('msystem', type: 'string', value: '',
+  description: 'Fall-back on Windows when MSYSTEM is not set.')
+option('mingw_prefix', type: 'string', value: '',
+  description: 'Fall-back on Windows when MINGW_PREFIX is not set.')
 
 # Build information compiled into Git and other parts like documentation.
 option('build_date', type: 'string', value: '',
diff --git a/t/t0060-path-utils.sh b/t/t0060-path-utils.sh
index 8545cdfab559b4..56faf5fe732ee0 100755
--- a/t/t0060-path-utils.sh
+++ b/t/t0060-path-utils.sh
@@ -602,7 +602,8 @@ test_expect_success !VALGRIND,RUNTIME_PREFIX,CAN_EXEC_IN_PWD 'RUNTIME_PREFIX wor
 	echo "echo HERE" | write_script pretend/libexec/git-core/git-here &&
 	GIT_EXEC_PATH= ./pretend/bin/git here >actual &&
 	echo HERE >expect &&
-	test_cmp expect actual'
+	test_cmp expect actual
+'
 
 test_expect_success !VALGRIND,RUNTIME_PREFIX,CAN_EXEC_IN_PWD '%(prefix)/ works' '
 	git config yes.path "%(prefix)/yes" &&
@@ -611,4 +612,34 @@ test_expect_success !VALGRIND,RUNTIME_PREFIX,CAN_EXEC_IN_PWD '%(prefix)/ works'
 	test_cmp expect actual
 '
 
+test_expect_success MINGW,RUNTIME_PREFIX 'MSYSTEM/PATH is adjusted if necessary' '
+	if test -z "$MINGW_PREFIX"
+	then
+		MINGW_PREFIX="/$(echo "${MSYSTEM:-MINGW64}" | tr A-Z a-z)"
+	fi &&
+	mkdir -p "$HOME"/bin pretend"$MINGW_PREFIX"/bin \
+		pretend"$MINGW_PREFIX"/libexec/git-core pretend/usr/bin &&
+	cp "$GIT_EXEC_PATH"/git.exe pretend"$MINGW_PREFIX"/bin/ &&
+	cp "$GIT_EXEC_PATH"/git.exe pretend"$MINGW_PREFIX"/libexec/git-core/ &&
+	# copy the .dll files, if any (happens when building via CMake)
+	if test -n "$(ls "$GIT_EXEC_PATH"/*.dll 2>/dev/null)"
+	then
+		cp "$GIT_EXEC_PATH"/*.dll pretend"$MINGW_PREFIX"/bin/ &&
+		cp "$GIT_EXEC_PATH"/*.dll pretend"$MINGW_PREFIX"/libexec/git-core/
+	fi &&
+	echo "env | grep MSYSTEM=" | write_script "$HOME"/bin/git-test-home &&
+	echo "echo ${MINGW_PREFIX#/}" | write_script pretend"$MINGW_PREFIX"/bin/git-test-bin &&
+	echo "echo usr" | write_script pretend/usr/bin/git-test-bin2 &&
+
+	(
+		MSYSTEM= &&
+		GIT_EXEC_PATH= &&
+		pretend"$MINGW_PREFIX"/libexec/git-core/git.exe test-home >actual &&
+		pretend"$MINGW_PREFIX"/libexec/git-core/git.exe test-bin >>actual &&
+		pretend"$MINGW_PREFIX"/bin/git.exe test-bin2 >>actual
+	) &&
+	test_write_lines MSYSTEM=$MSYSTEM "${MINGW_PREFIX#/}" usr >expect &&
+	test_cmp expect actual
+'
+
 test_done