diff --git a/Makefile b/Makefile
index a2762e583a1..a983a57fb51 100644
--- a/Makefile
+++ b/Makefile
@@ -4,8 +4,20 @@ all::
 # Import tree-wide shared Makefile behavior and libraries
 include shared.mak
 
+# == Makefile defines ==
+#
+# These defines change the behavior of the Makefile itself, but have
+# no impact on what it builds:
+#
 # Define V=1 to have a more verbose compile.
 #
+# == Portability and optional library defines ==
+#
+# These defines indicate what Git can expect from the OS, what
+# libraries are available etc. Much of this is auto-detected in
+# config.mak.uname, or in configure.ac when using the optional "make
+# configure && ./configure" (see INSTALL).
+#
 # Define SHELL_PATH to a POSIX shell if your /bin/sh is broken.
 #
 # Define SANE_TOOL_PATH to a colon-separated list of paths to prepend
@@ -30,68 +42,8 @@ include shared.mak
 #
 # Define NO_OPENSSL environment variable if you do not have OpenSSL.
 #
-# Define USE_LIBPCRE if you have and want to use libpcre. Various
-# commands such as log and grep offer runtime options to use
-# Perl-compatible regular expressions instead of standard or extended
-# POSIX regular expressions.
-#
-# Only libpcre version 2 is supported. USE_LIBPCRE2 is a synonym for
-# USE_LIBPCRE, support for the old USE_LIBPCRE1 has been removed.
-#
-# Define LIBPCREDIR=/foo/bar if your PCRE header and library files are
-# in /foo/bar/include and /foo/bar/lib directories.
-#
 # Define HAVE_ALLOCA_H if you have working alloca(3) defined in that header.
 #
-# Define NO_CURL if you do not have libcurl installed.  git-http-fetch and
-# git-http-push are not built, and you cannot use http:// and https://
-# transports (neither smart nor dumb).
-#
-# Define CURLDIR=/foo/bar if your curl header and library files are in
-# /foo/bar/include and /foo/bar/lib directories.
-#
-# Define CURL_CONFIG to curl's configuration program that prints information
-# about the library (e.g., its version number).  The default is 'curl-config'.
-#
-# Define CURL_LDFLAGS to specify flags that you need to link when using libcurl,
-# if you do not want to rely on the libraries provided by CURL_CONFIG.  The
-# default value is a result of `curl-config --libs`.  An example value for
-# CURL_LDFLAGS is as follows:
-#
-#     CURL_LDFLAGS=-lcurl
-#
-# Define NO_EXPAT if you do not have expat installed.  git-http-push is
-# not built, and you cannot push using http:// and https:// transports (dumb).
-#
-# Define EXPATDIR=/foo/bar if your expat header and library files are in
-# /foo/bar/include and /foo/bar/lib directories.
-#
-# Define EXPAT_NEEDS_XMLPARSE_H if you have an old version of expat (e.g.,
-# 1.1 or 1.2) that provides xmlparse.h instead of expat.h.
-#
-# Define NO_GETTEXT if you don't want Git output to be translated.
-# A translated Git requires GNU libintl or another gettext implementation,
-# plus libintl-perl at runtime.
-#
-# Define USE_GETTEXT_SCHEME and set it to 'fallthrough', if you don't trust
-# the installed gettext translation of the shell scripts output.
-#
-# Define HAVE_LIBCHARSET_H if you haven't set NO_GETTEXT and you can't
-# trust the langinfo.h's nl_langinfo(CODESET) function to return the
-# current character set. GNU and Solaris have a nl_langinfo(CODESET),
-# FreeBSD can use either, but MinGW and some others need to use
-# libcharset.h's locale_charset() instead.
-#
-# Define CHARSET_LIB to the library you need to link with in order to
-# use locale_charset() function.  On some platforms this needs to set to
-# -lcharset, on others to -liconv .
-#
-# Define LIBC_CONTAINS_LIBINTL if your gettext implementation doesn't
-# need -lintl when linking.
-#
-# Define NO_MSGFMT_EXTENDED_OPTIONS if your implementation of msgfmt
-# doesn't support GNU extensions like --check and --statistics
-#
 # Define HAVE_PATHS_H if you have paths.h and want to use the default PATH
 # it specifies.
 #
@@ -152,38 +104,6 @@ include shared.mak
 # and do not want to use Apple's CommonCrypto library.  This allows you
 # to provide your own OpenSSL library, for example from MacPorts.
 #
-# Define BLK_SHA1 environment variable to make use of the bundled
-# optimized C SHA1 routine.
-#
-# Define DC_SHA1 to enable the collision-detecting sha1
-# algorithm. This is slower, but may detect attempted collision attacks.
-#
-# Define DC_SHA1_EXTERNAL in addition to DC_SHA1 if you want to build / link
-# git with the external SHA1 collision-detect library.
-# Without this option, i.e. the default behavior is to build git with its
-# own built-in code (or submodule).
-#
-# Define DC_SHA1_SUBMODULE in addition to DC_SHA1 to use the
-# sha1collisiondetection shipped as a submodule instead of the
-# non-submodule copy in sha1dc/. This is an experimental option used
-# by the git project to migrate to using sha1collisiondetection as a
-# submodule.
-#
-# Define OPENSSL_SHA1 environment variable when running make to link
-# with the SHA1 routine from openssl library.
-#
-# Define SHA1_MAX_BLOCK_SIZE to limit the amount of data that will be hashed
-# in one call to the platform's SHA1_Update(). e.g. APPLE_COMMON_CRYPTO
-# wants 'SHA1_MAX_BLOCK_SIZE=1024L*1024L*1024L' defined.
-#
-# Define BLK_SHA256 to use the built-in SHA-256 routines.
-#
-# Define NETTLE_SHA256 to use the SHA-256 routines in libnettle.
-#
-# Define GCRYPT_SHA256 to use the SHA-256 routines in libgcrypt.
-#
-# Define OPENSSL_SHA256 to use the SHA-256 routines in OpenSSL.
-#
 # Define NEEDS_CRYPTO_WITH_SSL if you need -lcrypto when using -lssl (Darwin).
 #
 # Define NEEDS_SSL_WITH_CRYPTO if you need -lssl when using -lcrypto (Darwin).
@@ -489,6 +409,120 @@ include shared.mak
 # to the "<name>" of the corresponding `compat/fsmonitor/fsm-settings-<name>.c`
 # that implements the `fsm_os_settings__*()` routines.
 #
+# === Optional library: libintl ===
+#
+# Define NO_GETTEXT if you don't want Git output to be translated.
+# A translated Git requires GNU libintl or another gettext implementation,
+# plus libintl-perl at runtime.
+#
+# Define USE_GETTEXT_SCHEME and set it to 'fallthrough', if you don't trust
+# the installed gettext translation of the shell scripts output.
+#
+# Define HAVE_LIBCHARSET_H if you haven't set NO_GETTEXT and you can't
+# trust the langinfo.h's nl_langinfo(CODESET) function to return the
+# current character set. GNU and Solaris have a nl_langinfo(CODESET),
+# FreeBSD can use either, but MinGW and some others need to use
+# libcharset.h's locale_charset() instead.
+#
+# Define CHARSET_LIB to the library you need to link with in order to
+# use locale_charset() function.  On some platforms this needs to set to
+# -lcharset, on others to -liconv .
+#
+# Define LIBC_CONTAINS_LIBINTL if your gettext implementation doesn't
+# need -lintl when linking.
+#
+# Define NO_MSGFMT_EXTENDED_OPTIONS if your implementation of msgfmt
+# doesn't support GNU extensions like --check and --statistics
+#
+# === Optional library: libexpat ===
+#
+# Define NO_EXPAT if you do not have expat installed.  git-http-push is
+# not built, and you cannot push using http:// and https:// transports (dumb).
+#
+# Define EXPATDIR=/foo/bar if your expat header and library files are in
+# /foo/bar/include and /foo/bar/lib directories.
+#
+# Define EXPAT_NEEDS_XMLPARSE_H if you have an old version of expat (e.g.,
+# 1.1 or 1.2) that provides xmlparse.h instead of expat.h.
+
+# === Optional library: libcurl ===
+#
+# Define NO_CURL if you do not have libcurl installed.  git-http-fetch and
+# git-http-push are not built, and you cannot use http:// and https://
+# transports (neither smart nor dumb).
+#
+# Define CURLDIR=/foo/bar if your curl header and library files are in
+# /foo/bar/include and /foo/bar/lib directories.
+#
+# Define CURL_CONFIG to curl's configuration program that prints information
+# about the library (e.g., its version number).  The default is 'curl-config'.
+#
+# Define CURL_LDFLAGS to specify flags that you need to link when using libcurl,
+# if you do not want to rely on the libraries provided by CURL_CONFIG.  The
+# default value is a result of `curl-config --libs`.  An example value for
+# CURL_LDFLAGS is as follows:
+#
+#     CURL_LDFLAGS=-lcurl
+#
+# === Optional library: libpcre2 ===
+#
+# Define USE_LIBPCRE if you have and want to use libpcre. Various
+# commands such as log and grep offer runtime options to use
+# Perl-compatible regular expressions instead of standard or extended
+# POSIX regular expressions.
+#
+# Only libpcre version 2 is supported. USE_LIBPCRE2 is a synonym for
+# USE_LIBPCRE, support for the old USE_LIBPCRE1 has been removed.
+#
+# Define LIBPCREDIR=/foo/bar if your PCRE header and library files are
+# in /foo/bar/include and /foo/bar/lib directories.
+#
+# == SHA-1 and SHA-256 defines ==
+#
+# === SHA-1 backend ===
+#
+# ==== Options common to all SHA-1 implementations ====
+#
+# Define SHA1_MAX_BLOCK_SIZE to limit the amount of data that will be hashed
+# in one call to the platform's SHA1_Update(). e.g. APPLE_COMMON_CRYPTO
+# wants 'SHA1_MAX_BLOCK_SIZE=1024L*1024L*1024L' defined.
+#
+# ==== Options for the sha1collisiondetection implementation ====
+#
+# Define DC_SHA1 to enable the collision-detecting sha1
+# algorithm. This is slower, but may detect attempted collision attacks.
+#
+# Define DC_SHA1_EXTERNAL in addition to DC_SHA1 if you want to build / link
+# git with the external SHA1 collision-detect library.
+# Without this option, i.e. the default behavior is to build git with its
+# own built-in code (or submodule).
+#
+# Define DC_SHA1_SUBMODULE in addition to DC_SHA1 to use the
+# sha1collisiondetection shipped as a submodule instead of the
+# non-submodule copy in sha1dc/. This is an experimental option used
+# by the git project to migrate to using sha1collisiondetection as a
+# submodule.
+#
+# ==== Other SHA-1 implementations ====
+#
+# Define BLK_SHA1 environment variable to make use of the bundled
+# optimized C SHA1 routine.
+#
+# Define OPENSSL_SHA1 environment variable when running make to link
+# with the SHA1 routine from openssl library.
+#
+# === SHA-256 backend ===
+#
+# Define BLK_SHA256 to use the built-in SHA-256 routines.
+#
+# Define NETTLE_SHA256 to use the SHA-256 routines in libnettle.
+#
+# Define GCRYPT_SHA256 to use the SHA-256 routines in libgcrypt.
+#
+# Define OPENSSL_SHA256 to use the SHA-256 routines in OpenSSL.
+#
+# == DEVELOPER defines ==
+#
 # Define DEVELOPER to enable more compiler warnings. Compiler version
 # and family are auto detected, but could be overridden by defining
 # COMPILER_FEATURES (see config.mak.dev). You can still set
