Accelerate startup time of make
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In d85b0df (Makefile: use `find` to determine static header dependencies, 2014-08-25), we switched from a static list of header files to a dynamically-generated one, asking `find` to enumerate them. Back in those days, we did not use `$(LIB_H)` by default, and many a `make` implementation seems smart enough not to run that `find` command in that case, so it was deemed okay to run `find` for special targets requiring this macro. However, as of ebb7baf (Makefile: add a hdr-check target, 2018-09-19), $(LIB_H) is part of a global rule and therefore must be expanded. Meaning: this `find` command has to be run upon every `make` invocation. In the presence of many a worktree, this can tax the developers' patience quite a bit. Even in the absence of worktrees or other untracked files and directories, the cost of I/O to generate that list of header files is simply a lot larger than a simple `git ls-files` call. Therefore, just like in 3353397 (Makefile: ask "ls-files" to list source files if available, 2011-10-18), we now prefer to use `git ls-files` to enumerate the header files to enumerating them via `find`, falling back to the latter if the former failed (which would be the case e.g. in a worktree that was extracted from a source .tar file rather than from a clone of Git's sources). This has one notable consequence: we no longer include `command-list.h` in `LIB_H`, as it is a generated file, not a tracked one, but that is easily worked around. Of the three sites that use `LIB_H`, two (`LOCALIZED_C` and `CHK_HDRS`) already handle generated headers separately. In the third, the computed-dependency fallback, we can just add in a reference to $(GENERATED_H). Likewise, we no longer include not-yet-tracked header files in `LIB_H`. Given the speed improvements, these consequences seem a comparably small price to pay. Signed-off-by: Johannes Schindelin <[email protected]>
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This is the version that made it to |
orgads
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Thanks, @orgads! |
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Accelerate startup time of `make`
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There is a
findcall in theMakefileto list all the header files that is pretty expensive on Windows, especially in scenarios where there are multiple worktrees as subdirectories of the main worktree, or when there are unrelated worktrees under the main worktree.This patch already made it into git.git's
next, and I'd like to have it in Git for Windows early, to accelerate my own development (and that of others, too).