Add changelog

changelog/unreleased/do-not-replace-file-when-copying.md

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+Bugfix: Do not lose old revisions when overwriting a file during copy
+
+We no longer delete-and-upload targets of copy operations but rather
+add a new version with the source content.
+
+This makes "overwrite when copying" behave the same as "overwrite when uploading".
+
+Overwriting when moving a file still deletes the old file (moves it into the
+trash) and replaces the whole file including the revisions of the source file.
+
+https://github.com/cs3org/reva/pull/3896