Single-step signing command does not work as documented

[alexey-igrychev]

The command git signatures add --push v1.0.0 does not perform pull/merge and cannot be used as a single step.
Readme: https://github.com/hashbang/git-signatures#pullmergesignpush-against-origin-as-single-step.

Example

❌ git signatures add --push

$ git signatures add --push REF

Updated tag 'latest-signature' (was 910391335)
Enumerating objects: 6, done.
Counting objects: 100% (6/6), done.
Delta compression using up to 8 threads
Compressing objects: 100% (6/6), done.
Writing objects: 100% (6/6), 1.43 KiB | 1.43 MiB/s, done.
Total 6 (delta 1), reused 0 (delta 0), pack-reused 0
remote: Resolving deltas: 100% (1/1), done.
 + 4b72ca355...5fe9bf926 latest-signature -> latest-signature (forced update)
 ! [rejected]            refs/notes/signatures -> refs/notes/signatures (fetch first)
error: failed to push some refs to 'github.com:foo/bar.git'
hint: Updates were rejected because the remote contains work that you do
hint: not have locally. This is usually caused by another repository pushing
hint: to the same ref. You may want to first integrate the remote changes
hint: (e.g., 'git pull ...') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.

✔️ git signatures pull && git signatures add --push

$ git signatures pull
remote: Enumerating objects: 5, done.
remote: Counting objects: 100% (5/5), done.
remote: Compressing objects: 100% (3/3), done.
remote: Total 3 (delta 0), reused 3 (delta 0), pack-reused 0
Unpacking objects: 100% (3/3), 1.26 KiB | 647.00 KiB/s, done.
 * [new ref]             refs/notes/signatures -> refs/notes/origin/signatures
 * [new tag]             latest-signature      -> origin/latest-signature

$ git signatures add --push REF
Updated tag 'latest-signature' (was 5fe9bf926)
Enumerating objects: 8, done.
Counting objects: 100% (8/8), done.
Delta compression using up to 8 threads
Compressing objects: 100% (5/5), done.
Writing objects: 100% (5/5), 1.45 KiB | 1.45 MiB/s, done.
Total 5 (delta 1), reused 0 (delta 0), pack-reused 0
remote: Resolving deltas: 100% (1/1), done.
   4b72ca355..44cb65bd4  refs/notes/signatures -> refs/notes/signatures
 + 5fe9bf926...44cb65bd4 latest-signature -> latest-signature (forced update)