When installing an extension, the CLI must to select the correct
binary to download for the machine (see the
[`installBin` function](78c1d00ecc/pkg/cmd/extension/manager.go (L240))).
By default, the CLI will download a binary matching the current
machine's architecture.
However, to provide better support for Macs running on Apple
Silicon, it will
[fall back](78c1d00ecc/pkg/cmd/extension/manager.go (L267-L274))
from `darwin-arm64` to `darwin-amd64` if
[Rosetta](https://support.apple.com/en-gb/102527) (Apple's
compatibility layer) is installed.
If Rosetta isn't installed, this fallback doesn't happen, which
can lead to surprising and confusing results when one Mac has
Rosetta and another doesn't, because the extension will install
on one machine but not another.
In the situation where a `darwin-arm64` binary isn't available
but the CLI can't fall back to `amd64` because Rosetta isn't
installed, this updates our error message to suggest installing
Rosetta.
Closes https://github.com/cli/cli/issues/9592.
If the extension publishes an amd64 binary and Rosetta is available,
use that binary as it will most likely work.
If the extension publishes an arm64 binary, make sure to codesign it
after downloading so that the OS allows its execution.
- doing mkdir before `git init <dir>` is not necessary; git will
create the directory if it doesn't exist
- passing both `-C` and `--git-dir` is not needed for git invocations
- reading the current working directory isn't necessary for specifying
nested paths to operate in
- use `git add .` instead of explicitly naming all paths; we generate a
gitignore for binaries that we want to avoid adding
- generate cross-platform gitignore for Go binary extensions
- add helpers to simplify writing files, tests
