Fix git file history log order

[mbien]

To get a git log for a file, history entries can't be simply sorted by date. Common actions like rebase may change commit order, commits could also have the same commit date and still be valid etc.

This change adds a position field to the fetched history entries which is now used in the UI comparator instead of dates.

Comparisons between local and git history items still use timestamps.

first commit has the modifications, second is for cleanup in related files.

reproducer:

1. init git repo with 3 commits: INIT, B and A
   • (changes of A and B should not be in conflict so that commit order can be easily changed)
2. rebase the last two commits and swap B with A
3. git log should show INIT, A, B, the NB file history tab will show INIT, B, A which is not the correct log order
   • note: the git ->show history action does always show the correct order, this is about the history mutiview tab

This is a minimal attempt to resolve this issue. UI-wise we should probably do more and swap the revision and date columns (and probably don't allow to sort by date at all).

draft since i have to test this better and I might add a cleanup commit, feedback still welcome

[ebarboni]

LGTM, git log and UI are in the same order

[mbien]

this is currently breaking the date column ordering of subversion repos. Will need another pass.

[mbien]

that was just a rebase with no other changes. will add a fix for SVN/HG later. Is fairly trivial.

[mbien]

change was squashed into the first commit: diff: https://github.com/apache/netbeans/compare/a92363b67dbb43de5e3edb7bd78f101a5739cae5..08991c59f4f88c8ffeb70f5ed78a45408f04575c

msg:

Update SVN/HG history provider to return file history without order randomization (trivial HashMap -> LinkedHashMap change).

[mbien]

all green, manually tested file history for a SVN and HG project and it worked

thanks for the review! -> merging for NB 29