Auto merge of #6337 - bundler:segiddins/fail-gracefully-when-resetting-to-rev-fails, r=colby-swandale

[GitProxy] Fail gracefully when resetting to the given revision fails

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

See https://github.com/bundler/bundler/issues/6324 for context.

The problem was when a git gem referenced a branch, and you tried to install on a machine without the revision in the lockfile cached, Bundler would print the following error:

```
Git error: command `git reset --hard cb70aded58b9215a495f0509e49daef930eec478` in directory
/home/deivid/.rbenv/versions/2.5.0/lib/ruby/gems/2.5.0/bundler/gems/decidim-cb70aded58b9 has failed.
If this error persists you could try removing the cache directory
'/home/deivid/.rbenv/versions/2.5.0/lib/ruby/gems/2.5.0/cache/bundler/git/decidim-9495d3039168996748af12c0fdb04debdea10392'
```

The problem was that removing the cache directory doesn't help.

### What was your diagnosis of the problem?

My diagnosis was we needed to print a `RevisionNotFound` error when that `git reset --hard` failed.

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

My fix rescues git command failures resulting from that `git reset --hard` and re-raises a more appropriate error message:

```
Revision cb70aded58b9215a495f0509e49daef930eec478 does not exist in the repository https://github.com/decidim/decidim. Maybe you misspelled it?
```

### Why did you choose this fix out of the possible options?

I chose this fix because it didn't involve bubbling information up from the git proxy to the definition. Ideally we'd re-rescue this error somewhere and suggest a `bundle update --source`, but that can be done in a separate PR.

(cherry picked from commit 21c262a36da1d1b4bfb71acf4de31edc94d796e8)

2 files changed, 31 insertions, 2 deletions

diff --git a/lib/bundler/source/git/git_proxy.rb b/lib/bundler/source/git/git_proxy.rb
index c56dda66ea..cd964f7e56 100644
--- a/lib/bundler/source/git/git_proxy.rb
+++ b/lib/bundler/source/git/git_proxy.rb
@@ -131,7 +131,12 @@ module Bundler
           # method 2
           SharedHelpers.chdir(destination) do
             git_retry %(fetch --force --quiet --tags "#{path}")
-            git "reset --hard #{@revision}"
+
+            begin
+              git "reset --hard #{@revision}"
+            rescue GitCommandError
+              raise MissingGitRevisionError.new(@revision, URICredentialsFilter.credential_filtered_uri(uri))
+            end
 
             if submodules
               git_retry "submodule update --init --recursive"
diff --git a/spec/bundler/source/git/git_proxy_spec.rb b/spec/bundler/source/git/git_proxy_spec.rb
index d282a449a5..3a29c97461 100644
--- a/spec/bundler/source/git/git_proxy_spec.rb
+++ b/spec/bundler/source/git/git_proxy_spec.rb
@@ -1,8 +1,12 @@
 # frozen_string_literal: true
 
 RSpec.describe Bundler::Source::Git::GitProxy do
+  let(:path) { Pathname("path") }
   let(:uri) { "https://github.com/bundler/bundler.git" }
-  subject { described_class.new(Pathname("path"), uri, "HEAD") }
+  let(:ref) { "HEAD" }
+  let(:revision) { nil }
+  let(:git_source) { nil }
+  subject { described_class.new(path, uri, ref, revision, git_source) }
 
   context "with configured credentials" do
     it "adds username and password to URI" do
@@ -113,4 +117,24 @@ RSpec.describe Bundler::Source::Git::GitProxy do
       end
     end
   end
+
+  describe "#copy_to" do
+    let(:destination) { tmpdir("copy_to_path") }
+    let(:submodules) { false }
+
+    context "when given a SHA as a revision" do
+      let(:revision) { "abcd" * 10 }
+
+      it "fails gracefully when resetting to the revision fails" do
+        expect(subject).to receive(:git_retry).with(start_with("clone ")) { destination.mkpath }
+        expect(subject).to receive(:git_retry).with(start_with("fetch "))
+        expect(subject).to receive(:git).with("reset --hard #{revision}").and_raise(Bundler::Source::Git::GitCommandError, "command")
+        expect(subject).not_to receive(:git)
+
+        expect { subject.copy_to(destination, submodules) }.
+          to raise_error(Bundler::Source::Git::MissingGitRevisionError,
+            "Revision #{revision} does not exist in the repository #{uri}. Maybe you misspelled it?")
+      end
+    end
+  end
 end