feat(npm): install packages from git repositories

docs/dev-tools/backends/npm.md

@@ -29,6 +29,15 @@ For a scoped package, quote its full identifier, for example
 `mise use 'npm:@biomejs/biome'`. The package's executable name can differ from its
 registry name. mise installs CLI packages, not arbitrary libraries.
 
+To install from a git repository instead of the registry, use a git URL or a
+`github:`, `gitlab:` or `bitbucket:` shorthand. The version is the git ref
+(a tag, branch or commit), and `latest` is the repository's default branch:
+
+```sh
+mise use 'npm:git+https://github.com/owner/repo'
+mise use 'npm:github:owner/repo@v1.2.0'
+```
+
 If the project already declares Prettier in `package.json`, run that copy through
 a package script to keep its plugins and version aligned with the project.
 

e2e/backend/test_npm_git

@@ -0,0 +1,20 @@
+#!/usr/bin/env bash
+
+# npm: tools can be installed from a git repository instead of the registry.
+repo="$PWD/gitpkg"
+mkdir -p "$repo/bin"
+cat >"$repo/package.json" <<'JSON'
+{"name":"gitpkg","version":"1.0.0","bin":{"gitpkg":"bin/gitpkg.sh"}}
+JSON
+printf '#!/bin/sh\necho gitpkg-v1\n' >"$repo/bin/gitpkg.sh"
+chmod +x "$repo/bin/gitpkg.sh"
+git -C "$repo" init -q -b main
+git -C "$repo" -c user.name=t -c user.email=t@t add -A
+git -C "$repo" -c user.name=t -c user.email=t@t commit -q -m v1
+git -C "$repo" tag v1
+
+printf '#!/bin/sh\necho gitpkg-v2\n' >"$repo/bin/gitpkg.sh"
+git -C "$repo" -c user.name=t -c user.email=t@t commit -q -am v2
+
+assert_contains "mise x 'npm:git+file://$repo@latest' -- gitpkg" "gitpkg-v2"
+assert_contains "mise x 'npm:git+file://$repo@v1' -- gitpkg" "gitpkg-v1"