Vcs identity check

vcs-identity-check

Verify the VCS identity before committing so the commit is attributed correctly, and recommend commit signing when it isn't configured.

Procedure

1. Read the identity for the VCS in use:

   • git → git config --show-scope --get user.name and git config --show-scope --get user.email (--show-scope is git ≥2.26; it prints the scope — local / global / system — alongside the value);
   • hg → hg config ui.username, then split on the last <…> pair into name and email (e.g. Petr Korobeinikov <[email protected]> → name Petr Korobeinikov, email [email protected]); if there is no <…>, treat the whole string as name and the email as unset;
   • jj → jj config get user.name / user.email.

2. Check:

   • name is non-empty, has ≥2 whitespace-separated tokens, and is not a literal email. The two-token rule assumes First Last conventions; for users with a single-token mononym (some Indonesian or Icelandic naming patterns), accept the value on the user's explicit confirmation and skip this sub-check;
   • email is non-empty, contains exactly one @, with at least one character on each side.

3. Read signing config:

   • git → git config commit.gpgsign, git config tag.gpgsign, git config user.signingkey, git config gpg.format;
   • jj → jj config get signing.behavior and jj config get signing.backend.

   Classify into one of three states:

   • Configured — commit.gpgsign=true, user.signingkey non-empty, gpg.format set (missing tag.gpgsign=true is a soft warning, not broken);
   • Not configured — commit.gpgsign unset or false, and user.signingkey empty;
   • Broken — anything else (e.g. commit.gpgsign=true with empty user.signingkey) — commits will fail to sign at runtime.

   This step is informational and does not block the commit by itself.

4. Short-circuit when prior commits already match. If the same author has a prior commit in this repo whose signing intent matches the current config, skip the confirmation in step 5 and the signing recommendation — the user has implicitly validated this setup before by committing under it.

   For git, run git log -1 --author="<email>" --pretty=format:'%G?' and treat as a match when:

   • prior commit carries a signature (%G? ≠ N) and current signing is Configured; or
   • prior commit has no signature (%G? = N) and current signing is Not configured.

   This compares intent (sign / don't sign), not the key, so it works for GPG and SSH alike regardless of how user.signingkey is written (key ID, fingerprint, with or without 0x… prefix, or a public-key file path).

   Anything else — no prior commit by this author, Broken state, or non-git VCS — falls through to step 5.

5. Show the resolved values and ask the user to confirm — «<First> <Last> <email> (from <scope>) — correct order, no typo?». <scope> is what git reported (local / global / system); for hg/jj, name the source file if available, otherwise omit. Order can't be detected automatically; confirmation is required. In the same message:

   • signing Not configured → include the recommendation from the Signing section below;
   • signing Broken → name the inconsistent settings explicitly and treat it as fix-now, not a suggestion.

6. If any identity check fails or the user rejects, stop. Do not proceed to the commit.

Fix

• git, repo-local: git config --local user.name "First Last" (and user.email).
• git, global: same with --global.
• hg: [ui] username = First Last <[email protected]> in ~/.hgrc.
• jj: jj config set --user user.name "First Last" (and email).

Re-run the checks after fixing.

Signing

Signing commits is a good practice: it lets reviewers verify a commit really came from the stated author, and platforms like GitHub / GitLab / Gitea show a «Verified» badge on signed commits. Recommend it whenever it isn't configured.

Two formats; pick what fits the user's setup:

• GPG — the traditional path, works everywhere git is hosted; requires generating a GPG key and uploading the public key to the host's «GPG keys» settings.
• SSH — reuses an existing SSH key, no extra tooling beyond git ≥2.34 and ssh-keygen; fits well when GPG isn't already in use. Requires uploading the public key as a «signing key» (separate from the auth key) on the host.

Setup (git, global):

GPG:

git config --global gpg.format openpgp
git config --global user.signingkey "<KEY-ID>"
git config --global commit.gpgsign true
git config --global tag.gpgsign true

SSH:

git config --global gpg.format ssh
git config --global user.signingkey "<path-to-public-key>"
git config --global commit.gpgsign true
git config --global tag.gpgsign true

Then upload the public key to the host's signing-keys settings.