[PATCH 2/3] reftable: clarify zlib version dependency

3541411189 (reftable: reading/writing blocks, 2021-07-20) add a comment
explaining that a newer zlib version is required but being a little vague
about the specifics

make sure the zlib version is mentioned to aid on deciding to enable or
not the NO_UNCOMPRESS2 compatibility layer

Signed-off-by: Carlo Marcelo Arenas Belón <redacted>
---
Squashing this as part of a reroll of hn/reftable might be preferable

 reftable/block.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/reftable/block.c b/reftable/block.c
index 92f8e5abfa..eb5268dd3a 100644
--- a/reftable/block.c
+++ b/reftable/block.c

@@ -16,7 +16,9 @@ license that can be found in the LICENSE file or at
 #include <zlib.h>
 
 #ifdef NO_UNCOMPRESS2
-/* This is uncompress2, which is only available in zlib as of 2017.
+/*
+ * This is uncompress2, which is only available in zlib >= 1.2.9
+ * (released as of early 2017)
  */
 int uncompress2(Bytef *dest, uLongf *destLen, const Bytef *source,
 		uLong *sourceLen);

-- 
2.32.0.826.g286871f41a