Our documentation claims we support curl versions back to 7.19.5. But we can no longer compile with that version since adding an unconditional use of CURLOPT_RESOLVE in 511cfd3bff (http: add custom hostname to IP address resolutions, 2022-05-16). That feature wasn't added to libcurl until 7.21.3. We could add #ifdefs to make this work back to 7.19.5. But given that nobody noticed the compilation failure in the intervening two years, it makes more sense to bump the version in the documentation to 7.21.3 (which is itself over 13 years old). We could perhaps go forward even more (which would let us drop some cruft from git-curl-compat.h), but this should be an obviously safe jump, and we can move forward later. Note that user-visible syntax for CURLOPT_RESOLVE has grown new features in subsequent curl versions. Our documentation mentions "+" and "-" entries, which require more recent versions than 7.21.3. We could perhaps clarify that in our docs, but it's probably not worth cluttering them with restrictions of ancient curl versions. This is a backport of c28ee09503 (INSTALL: bump libcurl version to 7.21.3, 2024-04-02) into the `maint-2.39` branch. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>