[PATCH 0/2] maintenance: do not open console on Windows

[PATCH 0/2] maintenance: do not open console on Windows

[Derrick Stolee via GitGitGadget]

These two patches are cherry-picks of commits that have lived in
git-for-windows/git since 2019 when background maintenance was originally
introduced.

If we run the core Git project's version of background maintenance on a
Windows platform, then each background maintenance run will create a new
console window, visible to the user. This is due to quirks around how
Windows applications work: they require some parent application and will
create a console window if one does not exist.

This is solved by creating a new 'headless-git.exe' executable that knows
how to hide its own window. This isn't an appropriate change to make to
'git.exe' since that expects to be run within an existing console or
application.

 1. Patch 1 introduces the 'headless-git.exe' executable with the ability to
    hide its window.
 2. Patch 2 modifies the schtasks integration to use 'headless-git.exe'
    instead of 'git.exe'.

Thanks, -Stolee

Johannes Schindelin (2):
  win32: add a helper to run `git.exe` without a foreground window
  git maintenance: avoid console window in scheduled tasks on Windows

 Makefile                                   |   9 ++
 builtin/gc.c                               |   2 +-
 compat/win32/headless.c                    | 115 +++++++++++++++++++++
 config.mak.uname                           |   3 +
 contrib/buildsystems/CMakeLists.txt        |   9 ++
 contrib/buildsystems/Generators/Vcxproj.pm |   4 +-
 contrib/buildsystems/engine.pl             |   1 +
 7 files changed, 140 insertions(+), 3 deletions(-)
 create mode 100644 compat/win32/headless.c


base-commit: a82fb66fed250e16d3010c75404503bea3f0ab61
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1570%2Fderrickstolee%2Fheadless-git-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1570/derrickstolee/headless-git-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/1570
-- 
gitgitgadget

[PATCH 1/2] win32: add a helper to run `git.exe` without a foreground window

[Johannes Schindelin via GitGitGadget]

From: Johannes Schindelin <johannes.schindelin@gmx.de>

On Windows, there are two kinds of executables, console ones and
non-console ones. Git's executables are all console ones.

When launching the former e.g. in a scheduled task, a CMD window pops
up. This is not what we want for the tasks installed via the `git
maintenance` command.

To work around this, let's introduce `headless-git.exe`, which is a
non-console program that does _not_ pop up any window. All it does is to
re-launch `git.exe`, suppressing that console window, passing through
all command-line arguments as-are.

Helped-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
Helped-by: Yuyi Wang <Strawberry_Str@hotmail.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 Makefile                                   |   9 ++
 compat/win32/headless.c                    | 115 +++++++++++++++++++++
 config.mak.uname                           |   3 +
 contrib/buildsystems/CMakeLists.txt        |   9 ++
 contrib/buildsystems/Generators/Vcxproj.pm |   4 +-
 contrib/buildsystems/engine.pl             |   1 +
 6 files changed, 139 insertions(+), 2 deletions(-)
 create mode 100644 compat/win32/headless.c

diff --git a/Makefile b/Makefile
index fb541dedc9f..15b327b72b9 100644
--- a/Makefile
+++ b/Makefile
@@ -2779,6 +2779,13 @@ compat/nedmalloc/nedmalloc.sp compat/nedmalloc/nedmalloc.o: EXTRA_CPPFLAGS = \
 compat/nedmalloc/nedmalloc.sp: SP_EXTRA_FLAGS += -Wno-non-pointer-null
 endif
 
+headless-git.o: compat/win32/headless.c GIT-CFLAGS
+	$(QUIET_CC)$(CC) $(ALL_CFLAGS) $(COMPAT_CFLAGS) \
+		-fno-stack-protector -o $@ -c -Wall -Wwrite-strings $<
+
+headless-git$X: headless-git.o git.res GIT-LDFLAGS
+	$(QUIET_LINK)$(CC) $(ALL_CFLAGS) $(ALL_LDFLAGS) -mwindows -o $@ $< git.res
+
 git-%$X: %.o GIT-LDFLAGS $(GITLIBS)
 	$(QUIET_LINK)$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) $(filter %.o,$^) $(LIBS)
 
@@ -3652,6 +3659,7 @@ clean: profile-clean coverage-clean cocciclean
 	$(RM) po/git.pot po/git-core.pot
 	$(RM) git.res
 	$(RM) $(OBJECTS)
+	$(RM) headless-git.o
 	$(RM) $(LIB_FILE) $(XDIFF_LIB) $(REFTABLE_LIB) $(REFTABLE_TEST_LIB)
 	$(RM) $(ALL_PROGRAMS) $(SCRIPT_LIB) $(BUILT_INS) $(OTHER_PROGRAMS)
 	$(RM) $(TEST_PROGRAMS)
@@ -3680,6 +3688,7 @@ endif
 	$(RM) GIT-SCRIPT-DEFINES GIT-PERL-DEFINES GIT-PERL-HEADER GIT-PYTHON-VARS
 ifdef MSVC
 	$(RM) $(patsubst %.o,%.o.pdb,$(OBJECTS))
+	$(RM) headless-git.o.pdb
 	$(RM) $(patsubst %.exe,%.pdb,$(OTHER_PROGRAMS))
 	$(RM) $(patsubst %.exe,%.iobj,$(OTHER_PROGRAMS))
 	$(RM) $(patsubst %.exe,%.ipdb,$(OTHER_PROGRAMS))
diff --git a/compat/win32/headless.c b/compat/win32/headless.c
new file mode 100644
index 00000000000..8b00dfe3bd5
--- /dev/null
+++ b/compat/win32/headless.c
@@ -0,0 +1,115 @@
+/*
+ * headless Git - run Git without opening a console window on Windows
+ */
+
+#define STRICT
+#define WIN32_LEAN_AND_MEAN
+#define UNICODE
+#define _UNICODE
+#include <windows.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <wchar.h>
+
+/*
+ * If `dir` contains the path to a Git exec directory, extend `PATH` to
+ * include the corresponding `bin/` directory (which is where all those
+ * `.dll` files needed by `git.exe` are, on Windows).
+ */
+static int extend_path(wchar_t *dir, size_t dir_len)
+{
+	const wchar_t *suffix = L"\\libexec\\git-core";
+	size_t suffix_len = wcslen(suffix);
+	wchar_t *env;
+	DWORD len;
+
+	if (dir_len < suffix_len)
+		return 0;
+
+	dir_len -= suffix_len;
+	if (memcmp(dir + dir_len, suffix, suffix_len * sizeof(wchar_t)))
+		return 0;
+
+	len = GetEnvironmentVariableW(L"PATH", NULL, 0);
+	if (!len)
+		return 0;
+
+	env = _alloca((dir_len + 5 + len) * sizeof(wchar_t));
+	wcsncpy(env, dir, dir_len);
+	wcscpy(env + dir_len, L"\\bin;");
+	if (!GetEnvironmentVariableW(L"PATH", env + dir_len + 5, len))
+		return 0;
+
+	SetEnvironmentVariableW(L"PATH", env);
+	return 1;
+}
+
+int WINAPI wWinMain(_In_ HINSTANCE instance,
+		    _In_opt_ HINSTANCE previous_instance,
+		    _In_ LPWSTR command_line, _In_ int show)
+{
+	wchar_t git_command_line[32768];
+	size_t size = sizeof(git_command_line) / sizeof(wchar_t);
+	const wchar_t *needs_quotes = L"";
+	int slash = 0, i;
+
+	STARTUPINFO startup_info = {
+		.cb = sizeof(STARTUPINFO),
+		.dwFlags = STARTF_USESHOWWINDOW,
+		.wShowWindow = SW_HIDE,
+	};
+	PROCESS_INFORMATION process_info = { 0 };
+	DWORD creation_flags = CREATE_UNICODE_ENVIRONMENT |
+		CREATE_NEW_CONSOLE | CREATE_NO_WINDOW;
+	DWORD exit_code;
+
+	/* First, determine the full path of argv[0] */
+	for (i = 0; _wpgmptr[i]; i++)
+		if (_wpgmptr[i] == L' ')
+			needs_quotes = L"\"";
+		else if (_wpgmptr[i] == L'\\')
+			slash = i;
+
+	if (slash >= size - 11)
+		return 127; /* Too long path */
+
+	/* If it is in Git's exec path, add the bin/ directory to the PATH */
+	extend_path(_wpgmptr, slash);
+
+	/* Then, add the full path of `git.exe` as argv[0] */
+	i = swprintf_s(git_command_line, size, L"%ls%.*ls\\git.exe%ls",
+		       needs_quotes, slash, _wpgmptr, needs_quotes);
+	if (i < 0)
+		return 127; /* Too long path */
+
+	if (*command_line) {
+		/* Now, append the command-line arguments */
+		i = swprintf_s(git_command_line + i, size - i,
+			       L" %ls", command_line);
+		if (i < 0)
+			return 127;
+	}
+
+	startup_info.hStdInput = GetStdHandle(STD_INPUT_HANDLE);
+	startup_info.hStdOutput = GetStdHandle(STD_OUTPUT_HANDLE);
+	startup_info.hStdError = GetStdHandle(STD_ERROR_HANDLE);
+
+	if (!CreateProcess(NULL, /* infer argv[0] from the command line */
+			   git_command_line, /* modified command line */
+			   NULL, /* inherit process handles? */
+			   NULL, /* inherit thread handles? */
+			   FALSE, /* handles inheritable? */
+			   creation_flags,
+			   NULL, /* use this process' environment */
+			   NULL, /* use this process' working directory */
+			   &startup_info, &process_info))
+		return 129; /* could not start */
+	WaitForSingleObject(process_info.hProcess, INFINITE);
+	if (!GetExitCodeProcess(process_info.hProcess, &exit_code))
+		exit_code = 130; /* Could not determine exit code? */
+
+	CloseHandle(process_info.hProcess);
+	CloseHandle(process_info.hThread);
+
+	return (int)exit_code;
+}
diff --git a/config.mak.uname b/config.mak.uname
index 64c44db8058..3bb03f423a0 100644
--- a/config.mak.uname
+++ b/config.mak.uname
@@ -526,6 +526,8 @@ else
 endif
 	X = .exe
 
+	EXTRA_PROGRAMS += headless-git$X
+
 compat/msvc.o: compat/msvc.c compat/mingw.c GIT-CFLAGS
 endif
 ifeq ($(uname_S),Interix)
@@ -705,6 +707,7 @@ ifeq ($(uname_S),MINGW)
 	COMPAT_CFLAGS += -D__USE_MINGW_ANSI_STDIO=0 -DDETECT_MSYS_TTY \
 		-fstack-protector-strong
 	EXTLIBS += -lntdll
+	EXTRA_PROGRAMS += headless-git$X
 	INSTALL = /bin/install
 	INTERNAL_QSORT = YesPlease
 	HAVE_LIBCHARSET_H = YesPlease
diff --git a/contrib/buildsystems/CMakeLists.txt b/contrib/buildsystems/CMakeLists.txt
index 4faa419cc3d..6b819e2fbdf 100644
--- a/contrib/buildsystems/CMakeLists.txt
+++ b/contrib/buildsystems/CMakeLists.txt
@@ -738,6 +738,15 @@ if(WIN32)
 	else()
 		message(FATAL_ERROR "Unhandled compiler: ${CMAKE_C_COMPILER_ID}")
 	endif()
+
+	add_executable(headless-git ${CMAKE_SOURCE_DIR}/compat/win32/headless.c)
+	if(CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
+		target_link_options(headless-git PUBLIC -municode -Wl,-subsystem,windows)
+	elseif(CMAKE_C_COMPILER_ID STREQUAL "MSVC")
+		target_link_options(headless-git PUBLIC /NOLOGO /ENTRY:wWinMainCRTStartup /SUBSYSTEM:WINDOWS)
+	else()
+		message(FATAL_ERROR "Unhandled compiler: ${CMAKE_C_COMPILER_ID}")
+	endif()
 elseif(UNIX)
 	target_link_libraries(common-main pthread rt)
 endif()
diff --git a/contrib/buildsystems/Generators/Vcxproj.pm b/contrib/buildsystems/Generators/Vcxproj.pm
index 1a25789d285..b2e68a16715 100644
--- a/contrib/buildsystems/Generators/Vcxproj.pm
+++ b/contrib/buildsystems/Generators/Vcxproj.pm
@@ -76,7 +76,7 @@ sub createProject {
 
     my $libs_release = "\n    ";
     my $libs_debug = "\n    ";
-    if (!$static_library) {
+    if (!$static_library && $name ne 'headless-git') {
       $libs_release = join(";", sort(grep /^(?!libgit\.lib|xdiff\/lib\.lib|vcs-svn\/lib\.lib|reftable\/libreftable\.lib)/, @{$$build_structure{"$prefix${name}_LIBS"}}));
       $libs_debug = $libs_release;
       $libs_debug =~ s/zlib\.lib/zlibd\.lib/g;
@@ -230,7 +230,7 @@ EOM
     print F << "EOM";
   </ItemGroup>
 EOM
-    if (!$static_library || $target =~ 'vcs-svn' || $target =~ 'xdiff') {
+    if ((!$static_library || $target =~ 'vcs-svn' || $target =~ 'xdiff') && !($name =~ /headless-git/)) {
       my $uuid_libgit = $$build_structure{"LIBS_libgit_GUID"};
       my $uuid_libreftable = $$build_structure{"LIBS_reftable/libreftable_GUID"};
       my $uuid_xdiff_lib = $$build_structure{"LIBS_xdiff/lib_GUID"};
diff --git a/contrib/buildsystems/engine.pl b/contrib/buildsystems/engine.pl
index ed6c45988a3..069be7e4bef 100755
--- a/contrib/buildsystems/engine.pl
+++ b/contrib/buildsystems/engine.pl
@@ -371,6 +371,7 @@ sub handleLinkLine
 #    exit(1);
     foreach (@objfiles) {
         my $sourcefile = $_;
+        $sourcefile =~ s/^headless-git\.o$/compat\/win32\/headless.c/;
         $sourcefile =~ s/\.o$/.c/;
         push(@sources, $sourcefile);
         push(@cflags, @{$compile_options{"${sourcefile}_CFLAGS"}});
-- 
gitgitgadget

[PATCH 2/2] git maintenance: avoid console window in scheduled tasks on Windows

[Johannes Schindelin via GitGitGadget]

From: Johannes Schindelin <johannes.schindelin@gmx.de>

We just introduced a helper to avoid showing a console window when the
scheduled task runs `git.exe`. Let's actually use it.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 builtin/gc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/builtin/gc.c b/builtin/gc.c
index 19d73067aad..5c4315f0d81 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -2068,7 +2068,7 @@ static int schtasks_schedule_task(const char *exec_path, enum schedule_priority
 	      "</Settings>\n"
 	      "<Actions Context=\"Author\">\n"
 	      "<Exec>\n"
-	      "<Command>\"%s\\git.exe\"</Command>\n"
+	      "<Command>\"%s\\headless-git.exe\"</Command>\n"
 	      "<Arguments>--exec-path=\"%s\" for-each-repo --config=maintenance.repo maintenance run --schedule=%s</Arguments>\n"
 	      "</Exec>\n"
 	      "</Actions>\n"
-- 
gitgitgadget