[PATCH v2] Makefile: link osxkeychain & support universal Rust

From: Shnatu <snatu@google.com>

When Rust is enabled, ensure that the git-credential-osxkeychain helper is linked with the necessary Rust libraries.

Also, introduce native support for macOS Universal Binaries (multi-architecture builds) in the Git build system by allowing the user to specify a list of target triples in the RUST_TARGETS environment variable.

To implement this cleanly without complex shell scripting in recipes:
  1. We introduce a declarative Make pattern rule (target/%/...) to
     compile each target-specific library slice (e.g.,
     target/aarch64-apple-darwin/...).
  2. We update the $(RUST_LIB) recipe to depend on the list of
     compiled target-specific member libraries ($(RUST_MEMBER_LIBS)).
  3. On macOS, if multiple targets are specified, we use lipo to
     combine them into a single Universal static library at
     target/release/libgitcore.a.
  4. If only one target is specified, we copy it to the standard
     path.
  5. We enforce that building for multiple targets requires macOS
     (as lipo is only available there), raising a clear make error
     on other platforms.

This is a highly elegant and native Makefile solution that avoids complex shell scripting in recipes and fully supports macOS Universal Binaries.

Signed-off-by: Shardul Natu <snatu@google.com>
---
    Makefile: link osxkeychain helper against Rust

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2288%2Fkiranani%2Fnext-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2288/kiranani/next-v2
Pull-Request: https://github.com/git/git/pull/2288

Range-diff vs v1:

 1:  57046d2f78 ! 1:  6a11aff909 Makefile: link osxkeychain helper against Rust
     @@ Metadata
      Author: Shnatu <snatu@google.com>
      
       ## Commit message ##
     -    Makefile: link osxkeychain helper against Rust
     +    Makefile: link osxkeychain & support universal Rust
      
          When Rust is enabled, ensure that the git-credential-osxkeychain
          helper is linked with the necessary Rust libraries.
      
     -    Introduce the RUST_LIBS variable inside ifndef NO_RUST block
     -    to hold the Rust library dependency, and use it in the helper's
     -    build target. This cleanly handles cases where Rust is disabled,
     -    making it a no-op and avoiding any build failures on systems
     -    without Cargo.
     +    Also, introduce native support for macOS Universal Binaries
     +    (multi-architecture builds) in the Git build system by allowing
     +    the user to specify a list of target triples in the RUST_TARGETS
     +    environment variable.
      
     -    This addresses reviewer feedback from internal CL 910223487
     -    by simplifying the variables and avoiding confusing "LINK"
     -    terminology.
     +    To implement this cleanly without complex shell scripting in recipes:
     +      1. We introduce a declarative Make pattern rule (target/%/...) to
     +         compile each target-specific library slice (e.g.,
     +         target/aarch64-apple-darwin/...).
     +      2. We update the $(RUST_LIB) recipe to depend on the list of
     +         compiled target-specific member libraries ($(RUST_MEMBER_LIBS)).
     +      3. On macOS, if multiple targets are specified, we use lipo to
     +         combine them into a single Universal static library at
     +         target/release/libgitcore.a.
     +      4. If only one target is specified, we copy it to the standard
     +         path.
     +      5. We enforce that building for multiple targets requires macOS
     +         (as lipo is only available there), raising a clear make error
     +         on other platforms.
      
     -    Signed-off-by: Shnatu <snatu@google.com>
     +    This is a highly elegant and native Makefile solution that avoids
     +    complex shell scripting in recipes and fully supports macOS Universal
     +    Binaries.
     +
     +    Signed-off-by: Shardul Natu <snatu@google.com>
      
       ## Makefile ##
     -@@ Makefile: ALL_LDFLAGS = $(LDFLAGS) $(LDFLAGS_APPEND)
     - ifndef NO_RUST
     - BASIC_CFLAGS += -DWITH_RUST
     - GITLIBS += $(RUST_LIB)
     -+RUST_LIBS = $(RUST_LIB)
     +@@ Makefile: include shared.mak
     + #
     + # Building Rust code requires Cargo.
     + #
     ++# Define RUST_TARGETS if you want to cross-compile. If left unspecified, it uses
     ++# the default rust target on the system.
     ++#
     ++# On macOS, this supports specifying multiple targets, separated by a space.
     ++# This will produce a Universal static library using `lipo`.
     ++#
     ++# Example: RUST_TARGETS="aarch64-apple-darwin x86_64-apple-darwin"
     ++#
     + # == SHA-1 and SHA-256 defines ==
     + #
     + # === SHA-1 backend ===
     +@@ Makefile: TEST_SHELL_PATH = $(SHELL_PATH)
     + 
     + LIB_FILE = libgit.a
     + 
     ++ifndef NO_RUST
     + ifdef DEBUG
     +-RUST_TARGET_DIR = target/debug
     ++RUST_BUILD_CONFIG = debug
     + else
     +-RUST_TARGET_DIR = target/release
     ++RUST_BUILD_CONFIG = release
     + endif
     + 
       ifeq ($(uname_S),Windows)
     - EXTLIBS += -luserenv
     +-RUST_LIB = $(RUST_TARGET_DIR)/gitcore.lib
     ++RUST_LIB_NAME = gitcore.lib
     + else
     +-RUST_LIB = $(RUST_TARGET_DIR)/libgitcore.a
     ++RUST_LIB_NAME = libgitcore.a
     ++endif
     ++RUST_LIB = target/$(RUST_BUILD_CONFIG)/$(RUST_LIB_NAME)
       endif
     + 
     + GITLIBS = common-main.o $(LIB_FILE)
     +@@ Makefile: scalar$X: scalar.o GIT-LDFLAGS $(GITLIBS)
     + $(LIB_FILE): $(LIB_OBJS)
     + 	$(QUIET_AR)$(RM) $@ && $(AR) $(ARFLAGS) $@ $^
     + 
     ++ifndef NO_RUST
     ++ifeq ($(RUST_TARGETS),)
     + $(RUST_LIB): Cargo.toml $(RUST_SOURCES) $(LIB_FILE)
     + 	$(QUIET_CARGO)cargo build $(CARGO_ARGS)
     ++else
     ++ifneq ($(words $(RUST_TARGETS)),1)
     ++ifneq ($(uname_S),Darwin)
     ++$(error Building universal Rust libraries requires macOS (lipo is not available on $(uname_S)))
     ++endif
     ++endif
     ++
     ++RUST_MEMBER_LIBS = $(foreach target,$(RUST_TARGETS),target/$(target)/$(RUST_BUILD_CONFIG)/$(RUST_LIB_NAME))
     ++$(RUST_MEMBER_LIBS): target/%/$(RUST_BUILD_CONFIG)/$(RUST_LIB_NAME): Cargo.toml $(RUST_SOURCES) $(LIB_FILE)
     ++	$(QUIET_CARGO)cargo build $(CARGO_ARGS) --target $*
     ++
     ++$(RUST_LIB): $(RUST_MEMBER_LIBS)
     ++	$(QUIET_GEN)\
     ++	if [ $(words $(RUST_TARGETS)) -gt 1 ]; then \
     ++		lipo -create $^ -output $@; \
     ++	else \
     ++		cp $< $@; \
     ++	fi
     ++endif
     + 
     + .PHONY: rust
     + rust: $(RUST_LIB)
     ++endif
     + 
     + export DEFAULT_EDITOR DEFAULT_PAGER
     + 
      @@ Makefile: $(LIBGIT_HIDDEN_EXPORT): $(LIBGIT_PARTIAL_EXPORT)
       contrib/libgit-sys/libgitpub.a: $(LIBGIT_HIDDEN_EXPORT)
       	$(AR) $(ARFLAGS) $@ $^
       
      -contrib/credential/osxkeychain/git-credential-osxkeychain: contrib/credential/osxkeychain/git-credential-osxkeychain.o $(LIB_FILE) GIT-LDFLAGS
     -+contrib/credential/osxkeychain/git-credential-osxkeychain: contrib/credential/osxkeychain/git-credential-osxkeychain.o $(LIB_FILE) $(RUST_LIBS) GIT-LDFLAGS
     ++# When Rust is enabled, git-credential-osxkeychain depends on Rust symbols in $(RUST_LIB)
     ++contrib/credential/osxkeychain/git-credential-osxkeychain: contrib/credential/osxkeychain/git-credential-osxkeychain.o $(LIB_FILE) $(RUST_LIB) GIT-LDFLAGS
       	$(QUIET_LINK)$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) \
     --		$(filter %.o,$^) $(LIB_FILE) $(EXTLIBS) -framework Security -framework CoreFoundation
     -+		$(filter %.o,$^) $(LIB_FILE) $(RUST_LIBS) $(EXTLIBS) -framework Security -framework CoreFoundation
     + 		$(filter %.o,$^) $(LIBS) -framework Security -framework CoreFoundation
       
     - contrib/credential/osxkeychain/git-credential-osxkeychain.o: contrib/credential/osxkeychain/git-credential-osxkeychain.c GIT-CFLAGS
     - 	$(QUIET_LINK)$(CC) -o $@ -c $(dep_args) $(compdb_args) $(ALL_CFLAGS) $(EXTRA_CPPFLAGS) $<

 Makefile | 44 +++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 39 insertions(+), 5 deletions(-)