fetch: add a --prune-tags option and fetch.pruneTags config

Add a --prune-tags option to git-fetch, along with fetch.pruneTags config option and a -P shorthand (-p is --prune). This allows for doing any of: git fetch -p -P git fetch --prune --prune-tags git fetch -p -P origin git fetch --prune --prune-tags origin Or simply: git config fetch.prune true && git config fetch.pruneTags true && git fetch Instead of the much more verbose: git fetch --prune origin 'refs/tags/*:refs/tags/*' '+refs/heads/*:refs/remotes/origin/*' Before this feature it was painful to support the use-case of pulling from a repo which is having both its branches *and* tags deleted regularly, and have our local references to reflect upstream. At work we create deployment tags in the repo for each rollout, and there's *lots* of those, so they're archived within weeks for performance reasons. Without this change it's hard to centrally configure such repos in /etc/gitconfig (on servers that are only used for working with them). You need to set fetch.prune=true globally, and then for each repo: git -C {} config --replace-all remote.origin.fetch "refs/tags/*:refs/tags/*" "^\+*refs/tags/\*:refs/tags/\*$" Now I can simply set fetch.pruneTags=true in /etc/gitconfig as well, and users running "git pull" will automatically get the pruning semantics I want. Even though "git remote" has corresponding "prune" and "update --prune" subcommands I'm intentionally not adding a corresponding prune-tags or "update --prune --prune-tags" mode to that command. It's advertised (as noted in my recent "git remote doc: correct dangerous lies about what prune does") as only modifying remote tracking references, whereas any --prune-tags option is always going to modify what from the user's perspective is a local copy of the tag, since there's no such thing as a remote tracking tag. Ideally add_prune_tags_to_fetch_refspec() would be something that would use ALLOC_GROW() to grow the 'fetch` member of the 'remote' struct. Instead I'm realloc-ing remote->fetch and adding the tag_refspec to the end. The reason is that parse_{fetch,push}_refspec which allocate the refspec (ultimately remote->fetch) struct are called many places that don't have access to a 'remote' struct. It would be hard to change all their callsites to be amenable to carry around the bookkeeping variables required for dynamic allocation. All the other callers of the API first incrementally construct the string version of the refspec in remote->fetch_refspec via add_fetch_refspec(), before finally calling parse_fetch_refspec() via some variation of remote_get(). It's less of a pain to deal with the one special case that needs to modify already constructed refspecs than to chase down and change all the other callsites. The API I'm adding is intentionally not generalized because if we add more of these we'd probably want to re-visit how this is done. See my "Re: [BUG] git remote prune removes local tags, depending on fetch config" (87po6ahx87.fsf@evledraar.gmail.com; https://public-inbox.org/git/87po6ahx87.fsf@evledraar.gmail.com/) for more background info. Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>