How does 'git merge' work in details?

Question

I want to know an exact algorithm (or near that) behind \'git merge\'. The answers at least to these sub-questions will be helpful:

• How does git detect the con

Answer 1

How does git detect the context of a particular non-conflicting change?
How does git find out that there is a conflict in these exact lines?

If the same line has changed on both side of the merge, it's a conflict; if they haven't, the change from one side (if existent) is accepted.

Which things does git auto-merge?

Changes that do not conflict (see above)

How does git perform when there are multiple common bases for merging branches?

By the definition of a Git merge-base, there is only ever one (the latest common ancestor).

What happens when I merge multiple branches at once?

That depends on the merge strategy (only the octopus and the ours/theirs strategies support merging more than two branches).

What is a difference between merge strategies?

This is explained in the git merge manpage.