Merge pull request #15768 from carlocab/source-install-from-api

Revert "brew.sh: don't set `HOMEBREW_NO_INSTALL_FROM_API` automatically."

Library/Homebrew/brew.sh

@@ -533,6 +533,8 @@ then
   # shellcheck disable=SC2086,SC2183
   printf -v HOMEBREW_MACOS_VERSION_NUMERIC "%02d%02d%02d" ${HOMEBREW_MACOS_VERSION//./ }
   # shellcheck disable=SC2248
+  printf -v HOMEBREW_MACOS_OLDEST_SUPPORTED_NUMERIC "%02d%02d%02d" ${HOMEBREW_MACOS_OLDEST_SUPPORTED//./ }
+  # shellcheck disable=SC2248
   printf -v HOMEBREW_MACOS_OLDEST_ALLOWED_NUMERIC "%02d%02d%02d" ${HOMEBREW_MACOS_OLDEST_ALLOWED//./ }
 
   # Don't include minor versions for Big Sur and later.
@@ -591,6 +593,12 @@ then
     # shellcheck disable=SC2034
     HOMEBREW_MACOS_SYSTEM_RUBY_NEW_ENOUGH="1"
   fi
+
+  # Don't support API at this time for older macOS versions.
+  if [[ "${HOMEBREW_MACOS_VERSION_NUMERIC}" -lt "${HOMEBREW_MACOS_OLDEST_SUPPORTED_NUMERIC}" ]]
+  then
+    export HOMEBREW_NO_INSTALL_FROM_API=1
+  fi
 else
   HOMEBREW_PRODUCT="${HOMEBREW_SYSTEM}brew"
   [[ -n "${HOMEBREW_LINUX}" ]] && HOMEBREW_OS_VERSION="$(source /etc/os-release && echo "${PRETTY_NAME}")"
@@ -663,6 +671,12 @@ Your Git executable: $(unset git && type -p "${HOMEBREW_GIT}")"
   fi
 fi
 
+# Generic OS or non-default prefix: API not supported.
+if [[ (-z "${HOMEBREW_MACOS}" && -z "${HOMEBREW_LINUX}") || "${HOMEBREW_PREFIX}" != "${HOMEBREW_DEFAULT_PREFIX}" ]]
+then
+  export HOMEBREW_NO_INSTALL_FROM_API=1
+fi
+
 setup_ca_certificates() {
   if [[ -n "${HOMEBREW_FORCE_BREWED_CA_CERTIFICATES}" && -f "${HOMEBREW_PREFIX}/etc/ca-certificates/cert.pem" ]]
   then

docs/Installation.md

@@ -36,6 +36,8 @@ export HOMEBREW_NO_INSTALL_FROM_API=1
 
 This will make Homebrew install formulae and casks from the `homebrew/core` and `homebrew/cask` taps using local checkouts of these repositories instead of Homebrew’s API.
 
+Note that this will automatically be set on unsupported configurations (i.e. not using the default Homebrew prefix or, if on macOS, on an unsupported version).
+
 ## Unattended installation
 
 If you want a non-interactive run of the Homebrew installer that doesn't prompt for passwords (e.g. in automation scripts), prepend [`NONINTERACTIVE=1`](https://github.com/Homebrew/install/#install-homebrew-on-macos-or-linux) to the installation command.