On Wed, Sep 8, 2021 at 12:24 PM Johannes Schindelin via GitGitGadget <gitgitgadget@xxxxxxxxx> wrote: > > From: Johannes Schindelin <johannes.schindelin@xxxxxx> > > The idea of Scalar (https://github.com/microsoft/scalar), and before > that, of VFS for Git, has always been to prove that Git _can_ scale, and > to upstream whatever strategies have been demonstrated to help. > > With this patch, we start the journey from that C# project to move what > is left to Git's own `contrib/` directory, reimplementing it in pure C, > with the intention to facilitate integrating the functionality into core > Git all while maintaining backwards-compatibility for existing Scalar > users (which will be much easier when both live in the same worktree). > It was always to plan to contribute all of the proven strategies back to > core Git. s/always to plan/always the plan/ > For example, while the virtual filesystem provided by VFS for Git helped > the team developing the Windows operating system to move onto Git, while > trying to upstream it we realized that it cannot be done: getting the > virtual filesystem to work (which we only managed to implement fully on > Windows, but not on, say, macOS or Linux), and the required server-side > support for the GVFS protocol, made this not quite feasible. > > The Scalar project learned from that and tackled the problem with > different tactics: instead of pretending to Git that the working > directory is fully populated, it _specifically_ teaches Git about > partial clone (which is based on VFS for Git's cache server), about > sparse checkout (which VFS for Git tried to do transparently, in the > file system layer), and regularly runs maintenance tasks to keep the > repository in a healthy state. > > With partial clone, sparse checkout and `git maintenance` having been > upstreamed, there is little left that `scalar.exe` does that which > `git.exe` cannot do. One such thing is that `scalar clone <url>` will > automatically set up a partial, sparse clone, and configure > known-helpful settings from the start. s/does that which/does which/ > So let's bring this convenience into Git's tree. > > The idea here is that you can (optionally) build Scalar via > > make -C contrib/scalar/Makefile > > This will build the `scalar` executable and put it into the > contrib/scalar/ subdirectory. > > The slightly awkward addition of the `contrib/scalar/*` bits to the > top-level `Makefile` are actually really required: we want to link to > `libgit.a`, which means that we will need to use the very same `CFLAGS` > and `LDFLAGS` as the rest of Git. > > An early development version of this patch tried to replicate all the > conditional code in `contrib/scalar/Makefile` (e.g. `NO_POLL`) just like > `contrib/svn-fe/Makefile` used to do before it was retired. It turned > out to be quite the whack-a-mole game: the SHA-1-related flags, the > flags enabling/disabling `compat/poll/`, `compat/regex/`, > `compat/win32mmap.c` & friends depending on the current platform... To > put it mildly: it was a major mess. > > Instead, this patch makes minimal changes to the top-level `Makefile` so > that the bits in `contrib/scalar/` can be compiled and linked, and > adds a `contrib/scalar/Makefile` that uses the top-level `Makefile` in a > most minimal way to do the actual compiling. > > Note: With this commit, we only establish the infrastructure, no > Scalar functionality is implemented yet; We will do that incrementally > over the next few commits. > > Signed-off-by: Johannes Schindelin <johannes.schindelin@xxxxxx> > --- > Makefile | 8 ++++++++ > contrib/scalar/.gitignore | 2 ++ > contrib/scalar/Makefile | 34 ++++++++++++++++++++++++++++++++++ > contrib/scalar/scalar.c | 36 ++++++++++++++++++++++++++++++++++++ > 4 files changed, 80 insertions(+) > create mode 100644 contrib/scalar/.gitignore > create mode 100644 contrib/scalar/Makefile > create mode 100644 contrib/scalar/scalar.c > > diff --git a/Makefile b/Makefile > index c3565fc0f8f..2d5c822f7a8 100644 > --- a/Makefile > +++ b/Makefile > @@ -2447,6 +2447,10 @@ endif > .PHONY: objects > objects: $(OBJECTS) > > +SCALAR_SOURCES := contrib/scalar/scalar.c > +SCALAR_OBJECTS := $(SCALAR_SOURCES:c=o) > +OBJECTS += $(SCALAR_OBJECTS) > + > dep_files := $(foreach f,$(OBJECTS),$(dir $f).depend/$(notdir $f).d) > dep_dirs := $(addsuffix .depend,$(sort $(dir $(OBJECTS)))) > > @@ -2586,6 +2590,10 @@ $(REMOTE_CURL_PRIMARY): remote-curl.o http.o http-walker.o GIT-LDFLAGS $(GITLIBS > $(QUIET_LINK)$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) $(filter %.o,$^) \ > $(CURL_LIBCURL) $(EXPAT_LIBEXPAT) $(LIBS) > > +contrib/scalar/scalar$X: $(SCALAR_OBJECTS) GIT-LDFLAGS $(GITLIBS) > + $(QUIET_LINK)$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) \ > + $(filter %.o,$^) $(LIBS) > + > $(LIB_FILE): $(LIB_OBJS) > $(QUIET_AR)$(RM) $@ && $(AR) $(ARFLAGS) $@ $^ > > diff --git a/contrib/scalar/.gitignore b/contrib/scalar/.gitignore > new file mode 100644 > index 00000000000..ff3d47e84d0 > --- /dev/null > +++ b/contrib/scalar/.gitignore > @@ -0,0 +1,2 @@ > +/*.exe > +/scalar > diff --git a/contrib/scalar/Makefile b/contrib/scalar/Makefile > new file mode 100644 > index 00000000000..40c03ad10e1 > --- /dev/null > +++ b/contrib/scalar/Makefile > @@ -0,0 +1,34 @@ > +QUIET_SUBDIR0 = +$(MAKE) -C # space to separate -C and subdir > +QUIET_SUBDIR1 = > + > +ifneq ($(findstring s,$(MAKEFLAGS)),s) > +ifndef V > + QUIET_SUBDIR0 = +@subdir= > + QUIET_SUBDIR1 = ;$(NO_SUBDIR) echo ' ' SUBDIR $$subdir; \ > + $(MAKE) $(PRINT_DIR) -C $$subdir > +else > + export V > +endif > +endif > + > +all: > + > +include ../../config.mak.uname > +-include ../../config.mak.autogen > +-include ../../config.mak > + > +TARGETS = scalar$(X) scalar.o > +GITLIBS = ../../common-main.o ../../libgit.a ../../xdiff/lib.a > + > +all: scalar$X > + > +$(GITLIBS): > + $(QUIET_SUBDIR0)../.. $(QUIET_SUBDIR1) $(subst ../../,,$@) > + > +$(TARGETS): $(GITLIBS) scalar.c > + $(QUIET_SUBDIR0)../.. $(QUIET_SUBDIR1) $(patsubst %,contrib/scalar/%,$@) > + > +clean: > + $(RM) $(TARGETS) > + > +.PHONY: all clean FORCE > diff --git a/contrib/scalar/scalar.c b/contrib/scalar/scalar.c > new file mode 100644 > index 00000000000..7cff29e0fcd > --- /dev/null > +++ b/contrib/scalar/scalar.c > @@ -0,0 +1,36 @@ > +/* > + * The Scalar command-line interface. > + */ > + > +#include "cache.h" > +#include "gettext.h" > +#include "parse-options.h" > + > +static struct { > + const char *name; > + int (*fn)(int, const char **); > +} builtins[] = { > + { NULL, NULL}, > +}; > + > +int cmd_main(int argc, const char **argv) > +{ > + struct strbuf scalar_usage = STRBUF_INIT; > + int i; > + > + if (argc > 1) { > + argv++; > + argc--; > + > + for (i = 0; builtins[i].name; i++) > + if (!strcmp(builtins[i].name, argv[0])) > + return !!builtins[i].fn(argc, argv); > + } > + > + strbuf_addstr(&scalar_usage, > + N_("scalar <command> [<options>]\n\nCommands:\n")); > + for (i = 0; builtins[i].name; i++) > + strbuf_addf(&scalar_usage, "\t%s\n", builtins[i].name); > + > + usage(scalar_usage.buf); > +} > -- > gitgitgadget >
