Question

How i can use unison to sync folders with the latest modification time of its file

Example :-
folder_1/file.txt changed at 12:30
folder_2/file.txt changed at 12:35

i wanna execute ./unison to give me the following result :-
update file with regards to latest modification time so that update file folder_1/file.txt to became the same file folder_2.file.txt

Answer 1

You can’t.

Unison works by comparing both files with their last synchronized version. If both have changed, and the end result is not identical, they are marked as a conflict. Although in that case a merge program can be invoked to resolve the conflict, the modification time plays no role at all in the whole process.

From the manual:

Note that whether a path is updated has nothing to do with its last
modification time—Unison considers only the contents when determining
whether an update has occurred. This means that touching a file
without changing its contents will not be recognized as an update. A
file can even be changed several times and then changed back to its
original contents; as long as Unison is only run at the end of this
process, no update will be recognized.