On Tue, Dec 13, 2011 at 8:16 PM, Daniel Shahaf <d...@daniel.shahaf.name> wrote: > 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."
And even: $ svn mv some/file.txt some/otherfile.txt $ svn mv some/otherfile.txt some/file.txt $ svn ci -m "Replace some/file.txt with a copy of itself." (pre-1.7 this would be a replace without copyfrom, breaking the line of history [1], but that is fixed as of 1.7) [1] http://subversion.tigris.org/issues/show_bug.cgi?id=3429 - "svn mv A B; svn mv B A" generates replace without history -- Johan
