Can git SHA be displayed as part of a software version for an electronic device

Question

I would like to use and display a fairly standard semantic versioning MM.mm.bb = (M)ajor.(m)inor.(b)uild, but ideally I would like something computer generated, because I don't want to auto-increment the build number due to a peculiarity with this device.

I was thinking of trying to include the git SHA, but of course the SHA is not output until you form a commit.

Is it possible/reasonable to include the SHA in a software build version (for example: MM.mm.bb-f9a8e8)?

Given that I don't want to auto-increment build number and don't particularly want to add an additional SHA calculation other than the git one, Is there a better way to do this?

Answer 1

As I pointed out in the comments, Linux kernel does the trick. The main part there is the setlocalversion script, the core part of which is (detailed explanations are given inside the original script, below are only crucial parts)

    if test -z "$(git rev-parse --show-cdup 2>/dev/null)" &&
       head=$(git rev-parse --verify --short HEAD 2>/dev/null); then
            if [ -z "$(git describe --exact-match 2>/dev/null)" ]; then
                    printf '%s%s' -g $head
            fi

            if {
                    git --no-optional-locks status -uno --porcelain 2>/dev/null ||
                    git diff-index --name-only HEAD
            } | grep -qvE '^(.. )?scripts/package'; then
                    printf '%s' -dirty
            fi
    fi

Now our C file module.c:

#include <stdio.h>

#include "version.h"

int main(int argc, char *argv[])
{
    printf("Our version is: %s\n", VERSION);
    return 0;
}

and Makefile

VERSION = 0.1

version.h: FORCE
    @echo "$(VERSION)$(shell $(PWD)/setlocalversion $(PWD))"
    @echo "#define VERSION \"$(VERSION)$(shell $(PWD)/setlocalversion $(PWD))\"" > version.h


module.o: version.h

all: module
    @$(PWD)/module

clean:
    @rm module module.o version.h

FORCE:

.PHONY: FORCE

Show time:

$ make all
0.1-gb6d5c80
cc    -c -o module.o module.c
cc   module.o   -o module
Our version is: 0.1-gb6d5c80