v4, 10 partscompat: drop `uncompress2()` compatibility shim

Makefile, compat/zlib-uncompress2.c, git-compat-util.h, meson.build

diff --git a/Makefile b/Makefile
index 97e8385b66..86c6c3d7ad 100644
--- a/Makefile
+++ b/Makefile
@@ -984,7 +984,6 @@ LIB_OBJS += commit.o
 LIB_OBJS += compat/nonblock.o
 LIB_OBJS += compat/obstack.o
 LIB_OBJS += compat/terminal.o
-LIB_OBJS += compat/zlib-uncompress2.o
 LIB_OBJS += config.o
 LIB_OBJS += connect.o
 LIB_OBJS += connected.o
diff --git a/compat/zlib-uncompress2.c b/compat/zlib-uncompress2.c
deleted file mode 100644
index 77a1b08048..0000000000
--- a/compat/zlib-uncompress2.c
+++ /dev/null
@@ -1,96 +0,0 @@
-#include "git-compat-util.h"
-
-#if ZLIB_VERNUM < 0x1290
-/* taken from zlib's uncompr.c
-
-   commit cacf7f1d4e3d44d871b605da3b647f07d718623f
-   Author: Mark Adler <madler@alumni.caltech.edu>
-   Date:   Sun Jan 15 09:18:46 2017 -0800
-
-       zlib 1.2.11
-
-*/
-
-/*
- * Copyright (C) 1995-2003, 2010, 2014, 2016 Jean-loup Gailly, Mark Adler
- * For conditions of distribution and use, see copyright notice in zlib.h
- */
-
-/* clang-format off */
-
-/* ===========================================================================
-     Decompresses the source buffer into the destination buffer.  *sourceLen is
-   the byte length of the source buffer. Upon entry, *destLen is the total size
-   of the destination buffer, which must be large enough to hold the entire
-   uncompressed data. (The size of the uncompressed data must have been saved
-   previously by the compressor and transmitted to the decompressor by some
-   mechanism outside the scope of this compression library.) Upon exit,
-   *destLen is the size of the decompressed data and *sourceLen is the number
-   of source bytes consumed. Upon return, source + *sourceLen points to the
-   first unused input byte.
-
-     uncompress returns Z_OK if success, Z_MEM_ERROR if there was not enough
-   memory, Z_BUF_ERROR if there was not enough room in the output buffer, or
-   Z_DATA_ERROR if the input data was corrupted, including if the input data is
-   an incomplete zlib stream.
-*/
-int ZEXPORT uncompress2 (
-    Bytef *dest,
-    uLongf *destLen,
-    const Bytef *source,
-    uLong *sourceLen) {
-    z_stream stream;
-    int err;
-    const uInt max = (uInt)-1;
-    uLong len, left;
-    Byte buf[1];    /* for detection of incomplete stream when *destLen == 0 */
-
-    len = *sourceLen;
-    if (*destLen) {
-	left = *destLen;
-	*destLen = 0;
-    }
-    else {
-	left = 1;
-	dest = buf;
-    }
-
-    stream.next_in = (z_const Bytef *)source;
-    stream.avail_in = 0;
-    stream.zalloc = (alloc_func)0;
-    stream.zfree = (free_func)0;
-    stream.opaque = (voidpf)0;
-
-    err = inflateInit(&stream);
-    if (err != Z_OK) return err;
-
-    stream.next_out = dest;
-    stream.avail_out = 0;
-
-    do {
-	if (stream.avail_out == 0) {
-	    stream.avail_out = left > (uLong)max ? max : (uInt)left;
-	    left -= stream.avail_out;
-	}
-	if (stream.avail_in == 0) {
-	    stream.avail_in = len > (uLong)max ? max : (uInt)len;
-	    len -= stream.avail_in;
-	}
-	err = inflate(&stream, Z_NO_FLUSH);
-    } while (err == Z_OK);
-
-    *sourceLen -= len + stream.avail_in;
-    if (dest != buf)
-	*destLen = stream.total_out;
-    else if (stream.total_out && err == Z_BUF_ERROR)
-	left = 1;
-
-    inflateEnd(&stream);
-    return err == Z_STREAM_END ? Z_OK :
-	   err == Z_NEED_DICT ? Z_DATA_ERROR  :
-	   err == Z_BUF_ERROR && left + stream.avail_out ? Z_DATA_ERROR :
-	   err;
-}
-#else
-static void *dummy_variable = &dummy_variable;
-#endif
diff --git a/git-compat-util.h b/git-compat-util.h
index e283c46c6f..d50f487c00 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -1540,15 +1540,6 @@ int common_exit(const char *file, int line, int code);
 #define z_const
 #include <zlib.h>
 
-#if ZLIB_VERNUM < 0x1290
-/*
- * This is uncompress2, which is only available in zlib >= 1.2.9
- * (released as of early 2017). See compat/zlib-uncompress2.c.
- */
-int uncompress2(Bytef *dest, uLongf *destLen, const Bytef *source,
-		uLong *sourceLen);
-#endif
-
 /*
  * This include must come after system headers, since it introduces macros that
  * replace system names.
diff --git a/meson.build b/meson.build
index 30d7a89490..12129a8b95 100644
--- a/meson.build
+++ b/meson.build
@@ -263,7 +263,6 @@ libgit_sources = [
   'compat/nonblock.c',
   'compat/obstack.c',
   'compat/terminal.c',
-  'compat/zlib-uncompress2.c',
   'config.c',
   'connect.c',
   'connected.c',

diff --git a/git-compat-util.h b/git-compat-util.h
index d50f487c00..c4b4b372b4 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -1537,7 +1537,6 @@ int cmd_main(int, const char **);
 int common_exit(const char *file, int line, int code);
 #define exit(code) exit(common_exit(__FILE__, __LINE__, (code)))
 
-#define z_const
 #include <zlib.h>
 
 /*

compat/zlib-compat.h, git-compat-util.h, reftable/block.c

diff --git a/compat/zlib-compat.h b/compat/zlib-compat.h
new file mode 100644
index 0000000000..bc20b884ef
--- /dev/null
+++ b/compat/zlib-compat.h
@@ -0,0 +1,6 @@
+#ifndef COMPAT_ZLIB_H
+#define COMPAT_ZLIB_H
+
+#include <zlib.h>
+
+#endif /* COMPAT_ZLIB_H */
diff --git a/git-compat-util.h b/git-compat-util.h
index c4b4b372b4..1ca2671322 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -1537,7 +1537,7 @@ int cmd_main(int, const char **);
 int common_exit(const char *file, int line, int code);
 #define exit(code) exit(common_exit(__FILE__, __LINE__, (code)))
 
-#include <zlib.h>
+#include "compat/zlib-compat.h"
 
 /*
  * This include must come after system headers, since it introduces macros that
diff --git a/reftable/block.c b/reftable/block.c
index 9858bbc7c5..bc9b079634 100644
--- a/reftable/block.c
+++ b/reftable/block.c
@@ -13,7 +13,7 @@ license that can be found in the LICENSE file or at
 #include "record.h"
 #include "reftable-error.h"
 #include "system.h"
-#include <zlib.h>
+#include "compat/zlib-compat.h"
 
 int header_size(int version)
 {

archive.c, config.c, csum-file.c, environment.c, git-compat-util.h, git-zlib.h, reftable/block.c, reftable/system.h

diff --git a/archive.c b/archive.c
index b9c200cba6..8be4e7ac8d 100644
--- a/archive.c
+++ b/archive.c
@@ -7,6 +7,7 @@
 #include "convert.h"
 #include "environment.h"
 #include "gettext.h"
+#include "git-zlib.h"
 #include "hex.h"
 #include "object-name.h"
 #include "path.h"
diff --git a/config.c b/config.c
index 50f2d17b39..36f76fafe5 100644
--- a/config.c
+++ b/config.c
@@ -19,6 +19,7 @@
 #include "convert.h"
 #include "environment.h"
 #include "gettext.h"
+#include "git-zlib.h"
 #include "ident.h"
 #include "repository.h"
 #include "lockfile.h"
diff --git a/csum-file.c b/csum-file.c
index 5716016e12..78e04356d3 100644
--- a/csum-file.c
+++ b/csum-file.c
@@ -11,9 +11,10 @@
 #define USE_THE_REPOSITORY_VARIABLE
 
 #include "git-compat-util.h"
-#include "progress.h"
 #include "csum-file.h"
+#include "git-zlib.h"
 #include "hash.h"
+#include "progress.h"
 
 static void verify_buffer_or_die(struct hashfile *f,
 				 const void *buf,
diff --git a/environment.c b/environment.c
index 8389a27270..e5b361bb5d 100644
--- a/environment.c
+++ b/environment.c
@@ -16,6 +16,7 @@
 #include "convert.h"
 #include "environment.h"
 #include "gettext.h"
+#include "git-zlib.h"
 #include "repository.h"
 #include "config.h"
 #include "refs.h"
diff --git a/git-compat-util.h b/git-compat-util.h
index 1ca2671322..fb25fbf503 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -1537,8 +1537,6 @@ int cmd_main(int, const char **);
 int common_exit(const char *file, int line, int code);
 #define exit(code) exit(common_exit(__FILE__, __LINE__, (code)))
 
-#include "compat/zlib-compat.h"
-
 /*
  * This include must come after system headers, since it introduces macros that
  * replace system names.
diff --git a/git-zlib.h b/git-zlib.h
index d8a670aff9..1e8d9aabcb 100644
--- a/git-zlib.h
+++ b/git-zlib.h
@@ -1,6 +1,8 @@
 #ifndef GIT_ZLIB_H
 #define GIT_ZLIB_H
 
+#include "compat/zlib-compat.h"
+
 typedef struct git_zstream {
 	z_stream z;
 	unsigned long avail_in;
diff --git a/reftable/block.c b/reftable/block.c
index bc9b079634..38e3081c61 100644
--- a/reftable/block.c
+++ b/reftable/block.c
@@ -13,7 +13,6 @@ license that can be found in the LICENSE file or at
 #include "record.h"
 #include "reftable-error.h"
 #include "system.h"
-#include "compat/zlib-compat.h"
 
 int header_size(int version)
 {
diff --git a/reftable/system.h b/reftable/system.h
index 5274eca1d0..f194a38686 100644
--- a/reftable/system.h
+++ b/reftable/system.h
@@ -14,6 +14,7 @@ license that can be found in the LICENSE file or at
 #define DISABLE_SIGN_COMPARE_WARNINGS
 
 #include "git-compat-util.h"
+#include "compat/zlib-compat.h"
 
 /*
  * An implementation-specific temporary file. By making this specific to the

compat/zlib-compat.h, git-zlib.c

diff --git a/compat/zlib-compat.h b/compat/zlib-compat.h
index bc20b884ef..96a08811a9 100644
--- a/compat/zlib-compat.h
+++ b/compat/zlib-compat.h
@@ -3,4 +3,8 @@
 
 #include <zlib.h>
 
+#if defined(NO_DEFLATE_BOUND) || ZLIB_VERNUM < 0x1200
+# define deflateBound(c,s)  ((s) + (((s) + 7) >> 3) + (((s) + 63) >> 6) + 11)
+#endif
+
 #endif /* COMPAT_ZLIB_H */
diff --git a/git-zlib.c b/git-zlib.c
index d43bbeb6da..2e973320c2 100644
--- a/git-zlib.c
+++ b/git-zlib.c
@@ -147,10 +147,6 @@ int git_inflate(git_zstream *strm, int flush)
 	return status;
 }
 
-#if defined(NO_DEFLATE_BOUND) || ZLIB_VERNUM < 0x1200
-#define deflateBound(c,s)  ((s) + (((s) + 7) >> 3) + (((s) + 63) >> 6) + 11)
-#endif
-
 unsigned long git_deflate_bound(git_zstream *strm, unsigned long size)
 {
 	return deflateBound(&strm->z, size);

archive-tar.c, compat/zlib-compat.h

diff --git a/archive-tar.c b/archive-tar.c
index e7b3489e1e..0edf13fba7 100644
--- a/archive-tar.c
+++ b/archive-tar.c
@@ -473,9 +473,7 @@ static const char internal_gzip_command[] = "git archive gzip";
 static int write_tar_filter_archive(const struct archiver *ar,
 				    struct archiver_args *args)
 {
-#if ZLIB_VERNUM >= 0x1221
 	struct gz_header_s gzhead = { .os = 3 }; /* Unix, for reproducibility */
-#endif
 	struct strbuf cmd = STRBUF_INIT;
 	struct child_process filter = CHILD_PROCESS_INIT;
 	int r;
@@ -486,10 +484,8 @@ static int write_tar_filter_archive(const struct archiver *ar,
 	if (!strcmp(ar->filter_command, internal_gzip_command)) {
 		write_block = tgz_write_block;
 		git_deflate_init_gzip(&gzstream, args->compression_level);
-#if ZLIB_VERNUM >= 0x1221
 		if (deflateSetHeader(&gzstream.z, &gzhead) != Z_OK)
 			BUG("deflateSetHeader() called too late");
-#endif
 		gzstream.next_out = outbuf;
 		gzstream.avail_out = sizeof(outbuf);
 
diff --git a/compat/zlib-compat.h b/compat/zlib-compat.h
index 96a08811a9..6226b30c0c 100644
--- a/compat/zlib-compat.h
+++ b/compat/zlib-compat.h
@@ -7,4 +7,23 @@
 # define deflateBound(c,s)  ((s) + (((s) + 7) >> 3) + (((s) + 63) >> 6) + 11)
 #endif
 
+/*
+ * zlib only gained support for setting up the gzip header in v1.2.2.1. In
+ * Git we only set the header to make archives reproducible across different
+ * operating systems, so it's fine to simply make this a no-op when using a
+ * zlib version that doesn't support this yet.
+ */
+#if ZLIB_VERNUM < 0x1221
+struct gz_header_s {
+	int os;
+};
+
+static int deflateSetHeader(z_streamp strm, struct gz_header_s *head)
+{
+	(void)(strm);
+	(void)(head);
+	return Z_OK;
+}
+#endif
+
 #endif /* COMPAT_ZLIB_H */

diff --git a/git-zlib.c b/git-zlib.c
index 2e973320c2..651dd9e07c 100644
--- a/git-zlib.c
+++ b/git-zlib.c
@@ -59,7 +59,8 @@ static void zlib_post_call(git_zstream *s)
 
 	s->total_out = s->z.total_out;
 	s->total_in = s->z.total_in;
-	s->next_in = s->z.next_in;
+	/* zlib-ng marks `next_in` as `const`, so we have to cast it away. */
+	s->next_in = (unsigned char *) s->z.next_in;
 	s->next_out = s->z.next_out;
 	s->avail_in -= bytes_consumed;
 	s->avail_out -= bytes_produced;

Makefile, compat/zlib-compat.h, meson.build, meson_options.txt

diff --git a/Makefile b/Makefile
index 86c6c3d7ad..1853e6ddfa 100644
--- a/Makefile
+++ b/Makefile
@@ -183,7 +183,8 @@ include shared.mak
 # byte-order mark (BOM) when writing UTF-16 or UTF-32 and always writes in
 # big-endian format.
 #
-# Define NO_DEFLATE_BOUND if your zlib does not have deflateBound.
+# Define NO_DEFLATE_BOUND if your zlib does not have deflateBound. Define
+# ZLIB_NG if you want to use zlib-ng instead of zlib.
 #
 # Define NO_NORETURN if using buggy versions of gcc 4.6+ and profile feedback,
 # as the compiler can crash (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=49299)
@@ -1687,11 +1688,20 @@ else
 endif
 IMAP_SEND_LDFLAGS += $(OPENSSL_LINK) $(OPENSSL_LIBSSL) $(LIB_4_CRYPTO)
 
-ifdef ZLIB_PATH
-	BASIC_CFLAGS += -I$(ZLIB_PATH)/include
-	EXTLIBS += $(call libpath_template,$(ZLIB_PATH)/$(lib))
+ifdef ZLIB_NG
+	BASIC_CFLAGS += -DHAVE_ZLIB_NG
+	ifdef ZLIB_NG_PATH
+		BASIC_CFLAGS += -I$(ZLIB_NG_PATH)/include
+		EXTLIBS += $(call libpath_template,$(ZLIB_NG_PATH)/$(lib))
+	endif
+	EXTLIBS += -lz-ng
+else
+	ifdef ZLIB_PATH
+		BASIC_CFLAGS += -I$(ZLIB_PATH)/include
+		EXTLIBS += $(call libpath_template,$(ZLIB_PATH)/$(lib))
+	endif
+	EXTLIBS += -lz
 endif
-EXTLIBS += -lz
 
 ifndef NO_OPENSSL
 	OPENSSL_LIBSSL = -lssl
diff --git a/compat/zlib-compat.h b/compat/zlib-compat.h
index 6226b30c0c..0c60e3af33 100644
--- a/compat/zlib-compat.h
+++ b/compat/zlib-compat.h
@@ -1,11 +1,34 @@
 #ifndef COMPAT_ZLIB_H
 #define COMPAT_ZLIB_H
 
-#include <zlib.h>
+#ifdef HAVE_ZLIB_NG
+# include <zlib-ng.h>
 
-#if defined(NO_DEFLATE_BOUND) || ZLIB_VERNUM < 0x1200
-# define deflateBound(c,s)  ((s) + (((s) + 7) >> 3) + (((s) + 63) >> 6) + 11)
-#endif
+# define z_stream zng_stream
+#define gz_header_s zng_gz_header_s
+
+# define crc32(crc, buf, len) zng_crc32(crc, buf, len)
+
+# define inflate(strm, bits) zng_inflate(strm, bits)
+# define inflateEnd(strm) zng_inflateEnd(strm)
+# define inflateInit(strm) zng_inflateInit(strm)
+# define inflateInit2(strm, bits) zng_inflateInit2(strm, bits)
+# define inflateReset(strm) zng_inflateReset(strm)
+
+# define deflate(strm, flush) zng_deflate(strm, flush)
+# define deflateBound(strm, source_len) zng_deflateBound(strm, source_len)
+# define deflateEnd(strm) zng_deflateEnd(strm)
+# define deflateInit(strm, level) zng_deflateInit(strm, level)
+# define deflateInit2(stream, level, method, window_bits, mem_level, strategy) zng_deflateInit2(stream, level, method, window_bits, mem_level, strategy)
+# define deflateReset(strm) zng_deflateReset(strm)
+# define deflateSetHeader(strm, head) zng_deflateSetHeader(strm, head)
+
+#else
+# include <zlib.h>
+
+# if defined(NO_DEFLATE_BOUND) || ZLIB_VERNUM < 0x1200
+#  define deflateBound(c,s)  ((s) + (((s) + 7) >> 3) + (((s) + 63) >> 6) + 11)
+# endif
 
 /*
  * zlib only gained support for setting up the gzip header in v1.2.2.1. In
@@ -13,7 +36,7 @@
  * operating systems, so it's fine to simply make this a no-op when using a
  * zlib version that doesn't support this yet.
  */
-#if ZLIB_VERNUM < 0x1221
+# if ZLIB_VERNUM < 0x1221
 struct gz_header_s {
 	int os;
 };
@@ -24,6 +47,7 @@ static int deflateSetHeader(z_streamp strm, struct gz_header_s *head)
 	(void)(head);
 	return Z_OK;
 }
-#endif
+# endif
+#endif /* HAVE_ZLIB_NG */
 
 #endif /* COMPAT_ZLIB_H */
diff --git a/meson.build b/meson.build
index 12129a8b95..f9e6a051e0 100644
--- a/meson.build
+++ b/meson.build
@@ -792,11 +792,23 @@ else
   build_options_config.set('NO_PERL_CPAN_FALLBACKS', '')
 endif
 
-zlib = dependency('zlib', default_options: ['default_library=static', 'tests=disabled'])
-if zlib.version().version_compare('<1.2.0')
-  libgit_c_args += '-DNO_DEFLATE_BOUND'
+zlib_backend = get_option('zlib_backend')
+if zlib_backend in ['auto', 'zlib-ng']
+  zlib_ng = dependency('zlib-ng', required: zlib_backend == 'zlib-ng')
+  if zlib_ng.found()
+    zlib_backend = 'zlib-ng'
+    libgit_c_args += '-DHAVE_ZLIB_NG'
+    libgit_dependencies += zlib_ng
+  endif
+endif
+if zlib_backend in ['auto', 'zlib']
+  zlib = dependency('zlib', default_options: ['default_library=static', 'tests=disabled'])
+  if zlib.version().version_compare('<1.2.0')
+    libgit_c_args += '-DNO_DEFLATE_BOUND'
+  endif
+  zlib_backend = 'zlib'
+  libgit_dependencies += zlib
 endif
-libgit_dependencies += zlib
 
 threads = dependency('threads', required: false)
 if threads.found()
@@ -2001,4 +2013,5 @@ summary({
   'sha1': sha1_backend,
   'sha1_unsafe': sha1_unsafe_backend,
   'sha256': sha256_backend,
+  'zlib': zlib_backend,
 }, section: 'Backends')
diff --git a/meson_options.txt b/meson_options.txt
index 5429022f30..c962c0a676 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -57,6 +57,8 @@ option('sha1_unsafe_backend', type: 'combo', choices: ['openssl', 'block', 'Comm
   description: 'The backend used for hashing data with the SHA1 object format in case no cryptographic security is needed.')
 option('sha256_backend', type: 'combo', choices: ['openssl', 'nettle', 'gcrypt', 'block'], value: 'block',
   description: 'The backend used for hashing objects with the SHA256 object format.')
+option('zlib_backend', type: 'combo', choices: ['auto', 'zlib', 'zlib-ng'], value: 'auto',
+  description: 'The backend used for compressing objects and other data.')
 
 # Build tweaks.
 option('macos_use_homebrew_gettext', type: 'boolean', value: true,

.github/workflows/main.yml, .gitlab-ci.yml, ci/install-dependencies.sh, ci/lib.sh, ci/run-build-and-tests.sh, meson.build, meson_options.txt

diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 7f55f8b3a9..83bf9b918b 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -394,7 +394,7 @@ jobs:
       fail-fast: false
       matrix:
         vector:
-        - jobname: linux-musl
+        - jobname: linux-musl-meson
           image: alpine
           distro: alpine-latest
         # Supported until 2025-04-02.
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 4976e18a05..f737e4177c 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -67,7 +67,7 @@ test:linux:
         CC: clang
       - jobname: pedantic
         image: fedora:latest
-      - jobname: linux-musl
+      - jobname: linux-musl-meson
         image: alpine:latest
       - jobname: linux-meson
         image: ubuntu:latest
diff --git a/ci/install-dependencies.sh b/ci/install-dependencies.sh
index d1cb9fa878..5ae80b0486 100755
--- a/ci/install-dependencies.sh
+++ b/ci/install-dependencies.sh
@@ -24,7 +24,7 @@ fi
 
 case "$distro" in
 alpine-*)
-	apk add --update shadow sudo build-base curl-dev openssl-dev expat-dev gettext \
+	apk add --update shadow sudo meson ninja-build gcc libc-dev curl-dev openssl-dev expat-dev gettext \
 		pcre2-dev python3 musl-libintl perl-utils ncurses \
 		apache2 apache2-http2 apache2-proxy apache2-ssl apache2-webdav apr-util-dbd_sqlite3 \
 		bash cvs gnupg perl-cgi perl-dbd-sqlite perl-io-tty >/dev/null
diff --git a/ci/lib.sh b/ci/lib.sh
index 8885ee3c3f..71d85ae85a 100755
--- a/ci/lib.sh
+++ b/ci/lib.sh
@@ -378,10 +378,7 @@ linux32)
 	CC=gcc
 	;;
 linux-musl)
-	CC=gcc
-	MAKEFLAGS="$MAKEFLAGS PYTHON_PATH=/usr/bin/python3 USE_LIBPCRE2=Yes"
-	MAKEFLAGS="$MAKEFLAGS NO_REGEX=Yes ICONV_OMITS_BOM=Yes"
-	MAKEFLAGS="$MAKEFLAGS GIT_TEST_UTF8_LOCALE=C.UTF-8"
+	MESONFLAGS="$MESONFLAGS -DGIT_TEST_UTF8_LOCALE=C.UTF-8"
 	;;
 linux-leaks|linux-reftable-leaks)
 	export SANITIZE=leak
diff --git a/ci/run-build-and-tests.sh b/ci/run-build-and-tests.sh
index 964322055f..643c6a9dcc 100755
--- a/ci/run-build-and-tests.sh
+++ b/ci/run-build-and-tests.sh
@@ -55,7 +55,8 @@ case "$jobname" in
 		--fatal-meson-warnings \
 		--warnlevel 2 --werror \
 		--wrap-mode nofallback \
-		-Dfuzzers=true
+		-Dfuzzers=true \
+		$MESONFLAGS
 	group "Build" meson compile -C build --
 	if test -n "$run_tests"
 	then
diff --git a/meson.build b/meson.build
index f9e6a051e0..35b3c51fb1 100644
--- a/meson.build
+++ b/meson.build
@@ -664,7 +664,7 @@ build_options_config.set('GIT_TEST_CMP_USE_COPIED_CONTEXT', '')
 build_options_config.set('GIT_TEST_INDEX_VERSION', '')
 build_options_config.set('GIT_TEST_OPTS', '')
 build_options_config.set('GIT_TEST_PERL_FATAL_WARNINGS', '')
-build_options_config.set('GIT_TEST_UTF8_LOCALE', '')
+build_options_config.set_quoted('GIT_TEST_UTF8_LOCALE', get_option('test_utf8_locale'))
 build_options_config.set_quoted('LOCALEDIR', fs.as_posix(get_option('prefix') / get_option('localedir')))
 build_options_config.set('GITWEBDIR', fs.as_posix(get_option('prefix') / get_option('datadir') / 'gitweb'))
 
diff --git a/meson_options.txt b/meson_options.txt
index c962c0a676..e9f8e990e3 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -99,5 +99,7 @@ option('tests', type: 'boolean', value: true,
   description: 'Enable building tests. This requires Perl, but is separate from the "perl" option such that you can build tests without Perl features enabled.')
 option('test_output_directory', type: 'string',
   description: 'Path to the directory used to store test outputs')
+option('test_utf8_locale', type: 'string',
+  description: 'Name of a UTF-8 locale used for testing.')
 option('fuzzers', type: 'boolean', value: false,
   description: 'Enable building fuzzers.')

diff --git a/ci/install-dependencies.sh b/ci/install-dependencies.sh
index 5ae80b0486..be7ab4b1bf 100755
--- a/ci/install-dependencies.sh
+++ b/ci/install-dependencies.sh
@@ -25,7 +25,7 @@ fi
 case "$distro" in
 alpine-*)
 	apk add --update shadow sudo meson ninja-build gcc libc-dev curl-dev openssl-dev expat-dev gettext \
-		pcre2-dev python3 musl-libintl perl-utils ncurses \
+		zlib-ng-dev pcre2-dev python3 musl-libintl perl-utils ncurses \
 		apache2 apache2-http2 apache2-proxy apache2-ssl apache2-webdav apr-util-dbd_sqlite3 \
 		bash cvs gnupg perl-cgi perl-dbd-sqlite perl-io-tty >/dev/null
 	;;