Restore better error message when locked ref does not exist

[deivid-rodriguez]

What was the end-user or developer problem that led to this PR?

When user tries to install a Gemfile.lock file that includes a locked reference that does not exist, it will get a verbose and not too helpful error.

$ bundle install
Fetching gem metadata from https://rubygems.org/.
Fetching https://github.com/dependabot-fixtures/prius

Retrying `git fetch --force --quiet --no-tags --unshallow -- https://github.com/dependabot-fixtures/prius cff701b3bfb182afc99a85657d7c9f3d6c1ccce1:refs/cff701b3bfb182afc99a85657d7c9f3d6c1ccce1-sha` at /Users/deivid/Code/dependabot/dependabot-core/bundler/spec/fixtures/projects/bundler2/bad_ref/foo/ruby/3.2.0/cache/bundler/git/prius-17ebc9a1c48915a50268b9922f2901ebf171d281 due to error (2/4): Bundler::Source::Git::GitCommandError Git error: command `git fetch --force --quiet --no-tags --unshallow -- https://github.com/dependabot-fixtures/prius cff701b3bfb182afc99a85657d7c9f3d6c1ccce1:refs/cff701b3bfb182afc99a85657d7c9f3d6c1ccce1-sha` in directory /Users/deivid/Code/dependabot/dependabot-core/bundler/spec/fixtures/projects/bundler2/bad_ref/foo/ruby/3.2.0/cache/bundler/git/prius-17ebc9a1c48915a50268b9922f2901ebf171d281 has failed.
fatal: remote error: upload-pack: not our ref cff701b3bfb182afc99a85657d7c9f3d6c1ccce1

Retrying `git fetch --force --quiet --no-tags --unshallow -- https://github.com/dependabot-fixtures/prius cff701b3bfb182afc99a85657d7c9f3d6c1ccce1:refs/cff701b3bfb182afc99a85657d7c9f3d6c1ccce1-sha` at /Users/deivid/Code/dependabot/dependabot-core/bundler/spec/fixtures/projects/bundler2/bad_ref/foo/ruby/3.2.0/cache/bundler/git/prius-17ebc9a1c48915a50268b9922f2901ebf171d281 due to error (3/4): Bundler::Source::Git::GitCommandError Git error: command `git fetch --force --quiet --no-tags --unshallow -- https://github.com/dependabot-fixtures/prius cff701b3bfb182afc99a85657d7c9f3d6c1ccce1:refs/cff701b3bfb182afc99a85657d7c9f3d6c1ccce1-sha` in directory /Users/deivid/Code/dependabot/dependabot-core/bundler/spec/fixtures/projects/bundler2/bad_ref/foo/ruby/3.2.0/cache/bundler/git/prius-17ebc9a1c48915a50268b9922f2901ebf171d281 has failed.
fatal: remote error: upload-pack: not our ref cff701b3bfb182afc99a85657d7c9f3d6c1ccce1

Retrying `git fetch --force --quiet --no-tags --unshallow -- https://github.com/dependabot-fixtures/prius cff701b3bfb182afc99a85657d7c9f3d6c1ccce1:refs/cff701b3bfb182afc99a85657d7c9f3d6c1ccce1-sha` at /Users/deivid/Code/dependabot/dependabot-core/bundler/spec/fixtures/projects/bundler2/bad_ref/foo/ruby/3.2.0/cache/bundler/git/prius-17ebc9a1c48915a50268b9922f2901ebf171d281 due to error (4/4): Bundler::Source::Git::GitCommandError Git error: command `git fetch --force --quiet --no-tags --unshallow -- https://github.com/dependabot-fixtures/prius cff701b3bfb182afc99a85657d7c9f3d6c1ccce1:refs/cff701b3bfb182afc99a85657d7c9f3d6c1ccce1-sha` in directory /Users/deivid/Code/dependabot/dependabot-core/bundler/spec/fixtures/projects/bundler2/bad_ref/foo/ruby/3.2.0/cache/bundler/git/prius-17ebc9a1c48915a50268b9922f2901ebf171d281 has failed.
fatal: remote error: upload-pack: not our ref cff701b3bfb182afc99a85657d7c9f3d6c1ccce1

Git error: command `git fetch --force --quiet --no-tags --unshallow -- https://github.com/dependabot-fixtures/prius
cff701b3bfb182afc99a85657d7c9f3d6c1ccce1:refs/cff701b3bfb182afc99a85657d7c9f3d6c1ccce1-sha` in directory
/Users/deivid/Code/dependabot/dependabot-core/bundler/spec/fixtures/projects/bundler2/bad_ref/foo/ruby/3.2.0/cache/bundler/git/prius-17ebc9a1c48915a50268b9922f2901ebf171d281
has failed.
fatal: remote error: upload-pack: not our ref cff701b3bfb182afc99a85657d7c9f3d6c1ccce1

What is your fix for the problem, implemented in this PR?

My fix is to restore the kind of error Bundler 2.3 used to give:

$ bundle install
Fetching gem metadata from https://rubygems.org/.
Fetching https://github.com/dependabot-fixtures/prius

Git error: command `git fetch --force --quiet --no-tags --unshallow -- https://github.com/dependabot-fixtures/prius
cff701b3bfb182afc99a85657d7c9f3d6c1ccce1:refs/cff701b3bfb182afc99a85657d7c9f3d6c1ccce1-sha` in directory
/Users/deivid/Code/dependabot/dependabot-core/bundler/spec/fixtures/projects/bundler2/bad_ref/foo/ruby/3.2.0/cache/bundler/git/prius-17ebc9a1c48915a50268b9922f2901ebf171d281
has failed.
Revision cff701b3bfb182afc99a85657d7c9f3d6c1ccce1 does not exist in the repository https://github.com/dependabot-fixtures/prius. Maybe you misspelled it?

Make sure the following tasks are checked

• Describe the problem / feature
• Write tests for features and bug fixes
• Write code to solve the problem
• Make sure you follow the current code style and write meaningful commit messages without tags