Support self-hosted GitHub Enterprise

[joshuaspence]

Is your feature request related to a problem? Please describe.

I want to use Chezmoi to install various binaries from a self-hosted GitHub Enterprise installation. I am already using chezmoiexternals and the githubLatestRelease function to install binaries from github.com, for example:

---
.local/bin/chezmoi:
  type: 'file'
  executable: true
  url: '{{ (gitHubLatestRelease "twpayne/chezmoi").HTMLURL | replace "/releases/tag/" "/releases/download/" }}/chezmoi-{{ .chezmoi.os }}-{{ .chezmoi.arch }}'

But this doesn't work for self-hosted GitHub Enterprise as I don't believe there is a way to pass in a custom hostname. Similarly there isn't a way to pass in an auth token (there is $CHEZMOI_GITHUB_ACCESS_TOKEN but I would need a way to provide a token that is scoped to a single domain).

Describe the solution you'd like

Either a new family of functions (e.g. githubEnterpriseLatestRelease) or extending the existing GitHub functions to accept a hostname (e.g. githubLatestRelease "https://git.example.com/owner/repo"). Additionally, a way to provide the auth token for git.example.com in chezmoi.yaml.

Describe alternatives you've considered

Previously I was just using a script to do this:

#!/bin/bash

set -o errexit
set -o nounset
set -o pipefail

{{ $version := output "gh" "release" "--repo=git.example.com/owner/repo" "view" "--json=name" "--template={{.name}}" -}}
gh release --repo git.example.com/owner/repo download --output=- --pattern=example_{{ .chezmoi.os }}_{{ .chezmoi.arch }}.tar.gz {{ $version }} | tar --extract --file=- --gunzip --directory ~/.local/bin example

I have since changed to using a template since I want Chezmoi to purge unmanaged files from ~/.local/bin.

# dot_local/bin/executable_example.tmpl
{{- $version := output "gh" "--repo=git.example.com/owner/repo" "release" "view" "--json=name" "--jq=.name" | trim -}}
{{ output "sh" "-c" (printf "gh --repo=git.example.com/owner/repo release download --output=- --pattern=example_%s_%s.tar.gz %s | tar --extract --to-stdout --gunzip example" .chezmoi.os .chezmoi.arch $version) }}

This works okay, but seems a bit hacky and is definitely less readable.

I realize I could also do this using the git-repo external, but I would then need to add some sort is post-install script to do the actual compilation.