docs: describe remote.<name>.haveRefs config option

Document the new remote.<name>.haveRefs multi-valued config option in
Documentation/config/remote.adoc. Also update Documentation/fetch-options.adoc
to mention that --negotiation-tip restrictions do not apply to haveRefs.

Signed-off-by: Derrick Stolee <stolee@gmail.com>

Author: derrickstolee

Documentation/config/remote.adoc

@@ -107,6 +107,29 @@ priority configuration file (e.g. `.git/config` in a repository) to clear
 the values inherited from a lower priority configuration files (e.g.
 `$HOME/.gitconfig`).
 
+remote.<name>.haveRefs::
+	When negotiating with this remote during `git fetch` and `git push`,
+	the client advertises a list of commits that exist locally. In
+	repos with many references, this list of "haves" can be truncated.
+	Depending on data shape, dropping certain references may be
+	expensive. This multi-valued config option specifies ref patterns
+	whose tips should always be sent as "have" commits during fetch
+	negotiation with this remote.
++
+Each value is either an exact ref name (e.g. `refs/heads/release`) or a
+glob pattern (e.g. `refs/heads/release/*`). The pattern syntax is the same
+as for `--negotiation-tip`.
++
+If `--negotiation-tip` is used, then the have set is first restricted by
+that option and then increased to include the tips specified by the
+`remote.<name>.haveRefs` config values.
++
+This option is additive with the normal negotiation process: the
+negotiation algorithm still runs and advertises its own selected commits,
+but the refs matching `remote.<name>.haveRefs` are sent unconditionally on
+top of those heuristically selected commits. This option is also used
+during push negotiation when `push.negotiate` is enabled.
+
 remote.<name>.followRemoteHEAD::
 	How linkgit:git-fetch[1] should handle updates to `remotes/<name>/HEAD`
 	when fetching using the configured refspecs of a remote.

Documentation/fetch-options.adoc

@@ -67,7 +67,8 @@ this option multiple times, one for each matching ref name.
 +
 See also the `fetch.negotiationAlgorithm` and `push.negotiate`
 configuration variables documented in linkgit:git-config[1], and the
-`--negotiate-only` option below.
+`--negotiate-only` option below. Also, these restrictions do not apply
+to any `remote.<name>.haveRefs` config values.
 
 `--negotiate-only`::
 	Do not fetch anything from the server, and instead print the