On Mon, Mar 29, 2021 at 03:24:33PM -0700, Junio C Hamano wrote: > Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx> writes: > > > Refactor out the hard-to-read and maintain "ln || ln -s || cp" > > pattern. > > > > This was initially added in 3e073dc5611 (Makefile: always provide a > > fallback when hardlinks fail, 2008-08-25), but since then it's become > > a lot more complex as we've added: > > > > * 3426e34fedd (Add NO_CROSS_DIRECTORY_HARDLINKS support to the > > Makefile, 2009-05-11) > > > > * NO_INSTALL_HARDLINKS in 70de5e65e8c (Makefile: > > NO_INSTALL_HARDLINKS, 2012-05-02) > > > > * INSTALL_SYMLINKS in ad874608d8c (Makefile: optionally symlink > > libexec/git-core binaries to bin/git, 2018-03-13) > > > > * SKIP_DASHED_BUILT_INS 179227d6e21 (Optionally skip linking/copying > > the built-ins, 2020-09-21) > > > > Each of those commits had to add a new special-case to this code, > > resulting in quite an unmaintainable mess for adding any sort of new > > option. > > > > Let's use the newly introduced ln-or-cp.sh script instead, note that > > we only sometimes pass the --no-cross-directory-hardlinks option, per > > the previous behavior. The target of the "ln -s" is also another > > special snowflake, but we're careful to carry that forward. > > Nice. These explicit command-line options to the helper may be > harder to initially write and maintain than just exporting the > relevant $(MAKE) macros and using it from the helper, but once > it works correctly, it is much easier to see what is going on. Another option is to make "ln-or-cp" itself a target that "make" knows how to build, and bake the values into its "built" version. Besides making the invocations a bit shorter, it also means that the dependency graph is more correct. If a rule invokes ln-or-cp, its behavior will change if $NO_INSTALL_HARDLINKS changes, for example. Telling that to make requires depending on a sentinel file in each such caller (like GIT-BUILD-OPTIONS). Whereas we could do that once for the "ln-or-cp" target, and then everyone who uses it just depends on it. I had a series a long time ago that moved the whole Makefile in that direction, but I got nervous that it was too disruptive and too non-idiomatic to be worth pursuing. So I offer the alternative here mostly as food for thought. It may not be a good direction (and we already have good-enough solutions, like depending on GIT-BUILD-OPTIONS). -Peff
