git-crypt inconsistent handling of empty files [portability broken by OS patches]

[philpennock]

With two installs of git-crypt, both claiming to be 0.6.0, one on Ubuntu Focal (20.04) and one on an LXC container running Alpine Linux (so musl libc) 3.12.0, both with git-crypt installed from OS packages, I'm seeing conflicting behavior in handling an empty file.

ldd on Alpine

        /lib/ld-musl-x86_64.so.1 (0x7f3b96eea000)
        libcrypto.so.1.1 => /lib/libcrypto.so.1.1 (0x7f3b96c4c000)
        libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x7f3b96ab3000)
        libgcc_s.so.1 => /usr/lib/libgcc_s.so.1 (0x7f3b96a9f000)
        libc.musl-x86_64.so.1 => /lib/ld-musl-x86_64.so.1 (0x7f3b96eea000)

ldd on Ubuntu, package 0.6.0-1build2

	linux-vdso.so.1 (0x00007ffedad98000)
	libcrypto.so.1.1 => /lib/x86_64-linux-gnu/libcrypto.so.1.1 (0x00007ff7fbefe000)
	libstdc++.so.6 => /lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007ff7fbd1d000)
	libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007ff7fbd02000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007ff7fbb10000)
	libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007ff7fbb0a000)
	libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007ff7fbae7000)
	libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007ff7fb996000)
	/lib64/ld-linux-x86-64.so.2 (0x00007ff7fc225000)

git check-attr

% git check-attr -a homedir-links/_.mutt/server-certificates
homedir-links/_.mutt/server-certificates: diff: git-crypt
homedir-links/_.mutt/server-certificates: filter: git-crypt

With either version, if the other version last touched the file then this version shows M in git status but git diff can't show a diff. With the Ubuntu version, git cat-file -p $blobid shows encrypted content. With the Alpine version, the same shows that the file contents as committed to the repo are empty.

The Alpine OpenSSL is from package libcrypto1.1-1.1.1g-r0, the Ubuntu OpenSSL is from package libssl1.1-1.1.1f-1ubuntu2

At this point, my best guess is that some error return differs between musl and glibc and git-crypt doesn't handle them equivalently, and this uninformed speculation led to the issue title I've chosen.

[AGWA]

What's the version of Git on each system?

[AGWA]

It appears that the package on Alpine is not real git-crypt, but has been patched to handle empty files differently: https://git.alpinelinux.org/aports/tree/community/git-crypt/0002-keep-empty-files-unencrypted.patch

I will investigate whether I should apply this patch to git-crypt.

[philpennock]

Aargh, good catch, thank you. They've ... made git-crypt not compatible with itself. :(

[esantoro]

Hey @AGWA was this patch merged, by the way?

I'm having a lot of annoyances with empty .gitkeep files that are encrypted and pollute both commits and history.