I'm not familiar with Mercurial, so I don't understand the improvements the patch brings. Could you explain the benefits?
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Mercurial is very similar to git. I added another source to my repository, and when did pull from that source, unbelievably there is a revision without any commit message. When I wanted to fetch changesets, there was an exception (line that patched).
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Thank you, I understand the situation.

Can you please paste the error message in production.log？
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Go MAEDA wrote:
> Thank you, I understand the situation.
>
> Can you please paste the error message in production.log？

<pre>
Started GET "/projects/test/repository" for 31.57.0.155 at 2021-12-22 11:18:02 +0330
App 2260378 output: Processing by RepositoriesController#show as HTML
App 2260378 output: Parameters: {"id"=>"test"}
App 2260378 output: Current user: user (id=1)
App 2260378 output: Completed 500 Internal Server Error in 706ms (ActiveRecord: 6.4ms)
App 2260378 output:
App 2260378 output: TypeError (no implicit conversion of nil into String):
App 2260378 output:
App 2260378 output: lib/redmine/scm/adapters/mercurial_adapter.rb:233:in `unescape'
App 2260378 output: lib/redmine/scm/adapters/mercurial_adapter.rb:233:in `block in each_revision'
App 2260378 output: lib/redmine/scm/adapters/mercurial_adapter.rb:203:in `each'
App 2260378 output: lib/redmine/scm/adapters/mercurial_adapter.rb:203:in `each_revision'
App 2260378 output: app/models/repository/mercurial.rb:194:in `block in fetch_changesets'
App 2260378 output: app/models/repository/mercurial.rb:193:in `step'
App 2260378 output: app/models/repository/mercurial.rb:193:in `fetch_changesets'
App 2260378 output: app/controllers/repositories_controller.rb:87:in `show'
App 2260378 output: lib/redmine/sudo_mode.rb:61:in `sudo_mode'

</pre>
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I have confirmed this issue. Applying the patch(attachment:empty_message.diff) solved it. thank you.
I created @MercurialAdapterTest#test_empty_message@ because there was no test.
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