The remote heads to update from. This is relative to
$GIT_DIR (e.g. "HEAD", "refs/heads/master"). When
unspecified, update from all heads the remote side has.
++
+If the remote has enabled the options `uploadpack.allowTipSHA1InWant` or
+`uploadpack.allowReachableSHA1InWant`, they may alternatively be 40-hex
+sha1s present on the remote.
SEE ALSO
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