Improve autoupdate round 3

[lldelisle]

I found 2 bugs. First one is easy, if we do the | head -n 1 then even if there is no output it will be true. I proposed a fix which is to do the head -n 1 after. The second one is relatively hard. My strategy for workflows was that if the file CHANGELOG.md does not change, we do not push new commits but if it changes we force push. I forgot that the CHANGELOG.md contains the date... So if you run autoupdate on 2 different days it will consider changes while it is just the date which changed. I propose a fix which is to check if it is a workflow if there is a single line changing.

[lldelisle]

As I am writing a PR I incorporated 2 other changes:

• Avoid duplicated lines in CHANGELOG or body, for example https://github.com/galaxyproject/iwc/pull/527
• Add a message for the maintainers to know the strategy

[lldelisle]

Two other improvements:

• If there were errors, write an issue to the repo with the errors (this avoid to go to the log and check the last lines, especially for iwc where you need to download the whole log).
• If the autoupdate fails, get the last line of the stderr (for this, I need to send the stderr to a file but I think it is fine).

[lldelisle]

Let's hope it will not fill the inbox of people this time...