C. Michael Pilato wrote on Tue, Dec 13, 2011 at 14:01:45 -0500: > On 12/13/2011 01:25 PM, Eric S. Raymond wrote: > > C. Michael Pilato <cmpil...@collab.net>: > >>> Does a file replace differ in any way from a delete plus add of the new > >>> text? > >> > >> In Subversion, yes. A replacement is, like an add or a delete, an > >> operation > >> at the node level, not an operation on the contents of that node. A > >> replace > >> is an addition of a new object[1] -- with its own new line of version > >> control history -- that is coincidental with the removal of some previously > >> existing object that occupied the same path. > > > > I still don't understand how this differs from a delete followed by an add. > > Explain it to me like I'm reallllyyy stuuupid, please, so I can document it > > and you never have to explain it again. > > > > When I add a file at a given path, it creates new object with a > > history that is tracked. When I delete that path, I destroy the > > container as well as the content. If I subsequently create a new > > file at the same path, it's a new object with its own history. > > > > How is a replace different? > > Assume your "delete" and subsequent "add" happens in the same commit, it's > not different at all. In fact, the Subversion filesystem API doesn't even > recognize a "replace" operation. There's "delete (file or dir)", there's > "make file" and "make dir", and there's "copy (file or dir)". The "replace" > action found in the dumpfile is just a compacting of some delete operation > and a subsequent add or copy into a single verb, and that only because it > helps sequential processors of the dump stream avoid possibly notifying > about multiple actions on the same path. We favor the likes of: > > R /some/file.txt > > over: > > D /some/file.txt > A /some/file.txt > > in output. > > (My prior response was the result of my misreading your phrase "delete plus > add of the new text" as meaning "removing all the contents of the file, and > then adding all new contents of the same file". I see now that you were > talking about "container" operations, not content ones. Sorry about that.) > > >> [1] Most of the time. A replacement can have a copyfrom source, in which > >> case its not strictly a new line of history for that object. > > > > I think I get this part. When you replace with a copy source, you're > > destroying the container that existed at this path, abd replacing it with > > a new container that has history extending back through the copy source. > > Is that correct? > > Yup! > > I was trying to think through the generalities here, too. I believe they > boil down to this: > > "delete" stands alone. It never has text. Never has properties. > Never has copyfrom. > > "add" and "replace" can have text if the added object is a file. The > text is the contents of the added object as it appears in the committed > revision. "add" and "replace" of directories can not have text. > > "add and replace" can have properties -- the set of properties present > on the added file/directory in the committed revision. > > "add and replace" can have copyfrom information, indicating that the > "added" object does not truly represent the creation of a new line of > history, but is instead a continuation of a pre-existing line of > history. This is still an addition of sorts in that the object is newly > added to the set of its parent directory's list of children. > > But I haven't double-thunk that for complete accuracy. > > > So, everything except a delete can include properties and they all > > work the same way. Correct? > > Yes. > > >>> If a file replace can have a copyfrom source, how does replace with a > >>> copyfrom source differ from add with a copyfrom source? > >> > >> The differ only in the fact that a replace implies the simultaneous > >> deletion > >> of some other object which previously lived at that path. > > > > Got it. That case I understand, it's how they differ in the non-copyfrom > > case that still confuses me. > > This is replace without copyfrom: > > $ svn rm some/file.txt > $ touch some/file.txt > $ svn add some/file.txt > $ svn ci -m "Replace some/file.txt with a new file." > > This is replace with copyfrom: > > $ svn rm some/file.txt > $ touch some/file.txt > $ svn copy someother/differentfile.txt some/file.txt > $ svn ci -m "Replace some/file.txt with a copy of a different file ."
And: $ svn rm some/file.txt $ touch some/file.txt $ svn copy some/file.txt@HEAD some/file.txt $ svn ci -m "Replace some/file.txt with a copy itself."
