diff --git a/pkgs/applications/editors/ed/default.nix b/pkgs/applications/editors/ed/default.nix
index 37d055e2685..0fb48203b2f 100644
--- a/pkgs/applications/editors/ed/default.nix
+++ b/pkgs/applications/editors/ed/default.nix
@@ -1,6 +1,11 @@
 { stdenv, fetchurl, lzip
 }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 stdenv.mkDerivation (rec {
   name = "ed-${version}";
   version = "1.16";
diff --git a/pkgs/development/compilers/gcc/9/default.nix b/pkgs/development/compilers/gcc/9/default.nix
index 978ad75a3d2..5f0a69583a1 100644
--- a/pkgs/development/compilers/gcc/9/default.nix
+++ b/pkgs/development/compilers/gcc/9/default.nix
@@ -31,6 +31,11 @@
 , buildPackages
 }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 # LTO needs libelf and zlib.
 assert libelf != null -> zlib != null;
 
diff --git a/pkgs/development/interpreters/perl/default.nix b/pkgs/development/interpreters/perl/default.nix
index 9690dfac2f2..27ccb6f22c6 100644
--- a/pkgs/development/interpreters/perl/default.nix
+++ b/pkgs/development/interpreters/perl/default.nix
@@ -2,6 +2,11 @@
 , enableThreading ? true, coreutils, makeWrapper
 }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 with lib;
 
 let
diff --git a/pkgs/development/interpreters/python/cpython/default.nix b/pkgs/development/interpreters/python/cpython/default.nix
index e6c8b301c0b..d26d060da72 100644
--- a/pkgs/development/interpreters/python/cpython/default.nix
+++ b/pkgs/development/interpreters/python/cpython/default.nix
@@ -36,6 +36,11 @@
 , enableOptimizations ? (!stdenv.isDarwin)
 }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 assert x11Support -> tcl != null
                   && tk != null
                   && xorgproto != null
diff --git a/pkgs/development/libraries/acl/default.nix b/pkgs/development/libraries/acl/default.nix
index 4b280cc1862..6e863e4eeba 100644
--- a/pkgs/development/libraries/acl/default.nix
+++ b/pkgs/development/libraries/acl/default.nix
@@ -1,5 +1,10 @@
 { stdenv, fetchurl, gettext, attr }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 stdenv.mkDerivation rec {
   name = "acl-2.2.53";
 
diff --git a/pkgs/development/libraries/attr/default.nix b/pkgs/development/libraries/attr/default.nix
index 44eab6bc53c..d69d475f737 100644
--- a/pkgs/development/libraries/attr/default.nix
+++ b/pkgs/development/libraries/attr/default.nix
@@ -1,5 +1,10 @@
 { stdenv, fetchurl, gettext }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 stdenv.mkDerivation rec {
   name = "attr-2.4.48";
 
diff --git a/pkgs/development/libraries/c-ares/default.nix b/pkgs/development/libraries/c-ares/default.nix
index 02f0872cee3..2751565670a 100644
--- a/pkgs/development/libraries/c-ares/default.nix
+++ b/pkgs/development/libraries/c-ares/default.nix
@@ -1,5 +1,10 @@
 { stdenv, fetchurl, writeTextDir }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 let self =
 stdenv.mkDerivation rec {
   name = "c-ares-1.15.0";
diff --git a/pkgs/development/libraries/expat/default.nix b/pkgs/development/libraries/expat/default.nix
index 94aee7749ce..a356d7be1a9 100644
--- a/pkgs/development/libraries/expat/default.nix
+++ b/pkgs/development/libraries/expat/default.nix
@@ -1,5 +1,10 @@
 { stdenv, fetchurl }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 stdenv.mkDerivation rec {
   name = "expat-2.2.8";
 
diff --git a/pkgs/development/libraries/gettext/default.nix b/pkgs/development/libraries/gettext/default.nix
index 6adc147c6ac..46e52c7988e 100644
--- a/pkgs/development/libraries/gettext/default.nix
+++ b/pkgs/development/libraries/gettext/default.nix
@@ -1,5 +1,10 @@
 { stdenv, lib, fetchurl, libiconv, xz, fetchpatch }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 stdenv.mkDerivation rec {
   pname = "gettext";
   version = "0.20.1";
diff --git a/pkgs/development/libraries/glibc/common.nix b/pkgs/development/libraries/glibc/common.nix
index 8afea21729a..0b2f34c7b76 100644
--- a/pkgs/development/libraries/glibc/common.nix
+++ b/pkgs/development/libraries/glibc/common.nix
@@ -17,6 +17,11 @@
   but the exact set depends on the library version and the configuration.
 */
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 { stdenv, lib
 , buildPackages
 , fetchurl
diff --git a/pkgs/development/libraries/gmp/6.x.nix b/pkgs/development/libraries/gmp/6.x.nix
index c5fffa09bf0..f4432cfc5b8 100644
--- a/pkgs/development/libraries/gmp/6.x.nix
+++ b/pkgs/development/libraries/gmp/6.x.nix
@@ -3,6 +3,11 @@
 , buildPackages
 , withStatic ? false }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 let inherit (stdenv.lib) optional; in
 
 let self = stdenv.mkDerivation rec {
diff --git a/pkgs/development/libraries/kerberos/krb5.nix b/pkgs/development/libraries/kerberos/krb5.nix
index e5a593a7ff4..004d7d2227c 100644
--- a/pkgs/development/libraries/kerberos/krb5.nix
+++ b/pkgs/development/libraries/kerberos/krb5.nix
@@ -8,6 +8,11 @@
 , staticOnly ? false
 }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 let
   libOnly = type == "lib";
 in
diff --git a/pkgs/development/libraries/libelf/default.nix b/pkgs/development/libraries/libelf/default.nix
index 4e4afe96d54..2b56f973b5d 100644
--- a/pkgs/development/libraries/libelf/default.nix
+++ b/pkgs/development/libraries/libelf/default.nix
@@ -2,6 +2,11 @@
 , fetchurl, autoreconfHook, gettext
 }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 stdenv.mkDerivation rec {
   name = "libelf-0.8.13";
 
diff --git a/pkgs/development/libraries/libev/default.nix b/pkgs/development/libraries/libev/default.nix
index 74aa8133a99..1ea0615dc23 100644
--- a/pkgs/development/libraries/libev/default.nix
+++ b/pkgs/development/libraries/libev/default.nix
@@ -1,5 +1,10 @@
 { stdenv, fetchurl, static ? false }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 stdenv.mkDerivation rec {
   pname = "libev";
   version="4.33";
diff --git a/pkgs/development/libraries/libffi/default.nix b/pkgs/development/libraries/libffi/default.nix
index eecffeba23d..d7dad6d956d 100644
--- a/pkgs/development/libraries/libffi/default.nix
+++ b/pkgs/development/libraries/libffi/default.nix
@@ -3,6 +3,11 @@
 
 }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 stdenv.mkDerivation rec {
   name = "libffi-3.3";
 
diff --git a/pkgs/development/libraries/libidn2/default.nix b/pkgs/development/libraries/libidn2/default.nix
index 1fc0bd9b399..c5af2d16bb2 100644
--- a/pkgs/development/libraries/libidn2/default.nix
+++ b/pkgs/development/libraries/libidn2/default.nix
@@ -1,5 +1,10 @@
 { fetchurl, stdenv, libiconv, libunistring, help2man, buildPackages }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 with stdenv.lib;
 
 stdenv.mkDerivation rec {
diff --git a/pkgs/development/libraries/libmpc/default.nix b/pkgs/development/libraries/libmpc/default.nix
index 235474c0ca1..c0459e393fa 100644
--- a/pkgs/development/libraries/libmpc/default.nix
+++ b/pkgs/development/libraries/libmpc/default.nix
@@ -2,6 +2,11 @@
 , gmp, mpfr
 }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 let
   version = "1.1.0";
 in
diff --git a/pkgs/development/libraries/libunistring/default.nix b/pkgs/development/libraries/libunistring/default.nix
index f0cc73ba4e9..5f300ef5199 100644
--- a/pkgs/development/libraries/libunistring/default.nix
+++ b/pkgs/development/libraries/libunistring/default.nix
@@ -1,5 +1,10 @@
 { fetchurl, stdenv, libiconv }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 stdenv.mkDerivation rec {
   pname = "libunistring";
   version = "0.9.10";
diff --git a/pkgs/development/libraries/mpfr/default.nix b/pkgs/development/libraries/mpfr/default.nix
index ceba71ae06a..9fc717ef38a 100644
--- a/pkgs/development/libraries/mpfr/default.nix
+++ b/pkgs/development/libraries/mpfr/default.nix
@@ -1,5 +1,10 @@
 { stdenv, fetchurl, gmp }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 stdenv.mkDerivation rec {
   version = "4.0.2";
   pname = "mpfr";
diff --git a/pkgs/development/libraries/nghttp2/default.nix b/pkgs/development/libraries/nghttp2/default.nix
index 939f137ac3e..3294674e178 100644
--- a/pkgs/development/libraries/nghttp2/default.nix
+++ b/pkgs/development/libraries/nghttp2/default.nix
@@ -12,6 +12,11 @@
 , enablePython ? false, python ? null, cython ? null, ncurses ? null, setuptools ? null
 }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 assert enableHpack -> jansson != null;
 assert enableAsioLib -> boost != null;
 assert enableGetAssets -> libxml2 != null;
diff --git a/pkgs/development/libraries/openssl/default.nix b/pkgs/development/libraries/openssl/default.nix
index 43170f25d38..1fc38dd8aaa 100644
--- a/pkgs/development/libraries/openssl/default.nix
+++ b/pkgs/development/libraries/openssl/default.nix
@@ -5,6 +5,11 @@
 , static ? false
 }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 with stdenv.lib;
 
 let
diff --git a/pkgs/development/libraries/zlib/default.nix b/pkgs/development/libraries/zlib/default.nix
index c4a4c497ced..98746968146 100644
--- a/pkgs/development/libraries/zlib/default.nix
+++ b/pkgs/development/libraries/zlib/default.nix
@@ -12,6 +12,11 @@
 , splitStaticOutput ? static
 }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 assert splitStaticOutput -> static;
 
 stdenv.mkDerivation (rec {
diff --git a/pkgs/development/tools/misc/autoconf/default.nix b/pkgs/development/tools/misc/autoconf/default.nix
index 500d80d4bb8..93add837290 100644
--- a/pkgs/development/tools/misc/autoconf/default.nix
+++ b/pkgs/development/tools/misc/autoconf/default.nix
@@ -1,5 +1,10 @@
 { stdenv, fetchurl, m4, perl }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 stdenv.mkDerivation rec {
   name = "autoconf-2.69";
 
diff --git a/pkgs/development/tools/misc/binutils/default.nix b/pkgs/development/tools/misc/binutils/default.nix
index cd05ea354ca..b352e63a27c 100644
--- a/pkgs/development/tools/misc/binutils/default.nix
+++ b/pkgs/development/tools/misc/binutils/default.nix
@@ -10,6 +10,11 @@
 , texinfo
 }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 let
   reuseLibs = enableShared && withAllTargets;
 
diff --git a/pkgs/development/tools/misc/gnum4/default.nix b/pkgs/development/tools/misc/gnum4/default.nix
index b301324e956..2e3e4acfdc1 100644
--- a/pkgs/development/tools/misc/gnum4/default.nix
+++ b/pkgs/development/tools/misc/gnum4/default.nix
@@ -1,5 +1,10 @@
 { stdenv, fetchurl }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 stdenv.mkDerivation {
   name = "gnum4-1.4.18";
 
diff --git a/pkgs/development/tools/misc/help2man/default.nix b/pkgs/development/tools/misc/help2man/default.nix
index 74ba7f55093..f23b5a9c8fd 100644
--- a/pkgs/development/tools/misc/help2man/default.nix
+++ b/pkgs/development/tools/misc/help2man/default.nix
@@ -1,5 +1,10 @@
 { stdenv, fetchurl, perlPackages, gettext }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 stdenv.mkDerivation rec {
   name = "help2man-1.47.16";
 
diff --git a/pkgs/development/tools/misc/libtool/default.nix b/pkgs/development/tools/misc/libtool/default.nix
index debc4107882..199c6504f39 100644
--- a/pkgs/development/tools/misc/libtool/default.nix
+++ b/pkgs/development/tools/misc/libtool/default.nix
@@ -1,5 +1,10 @@
 {stdenv, fetchurl, m4, perl}:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 stdenv.mkDerivation rec {
   name = "libtool-1.5.26";
 
diff --git a/pkgs/development/tools/misc/patchelf/default.nix b/pkgs/development/tools/misc/patchelf/default.nix
index 5119225d9ae..5d2309333a6 100644
--- a/pkgs/development/tools/misc/patchelf/default.nix
+++ b/pkgs/development/tools/misc/patchelf/default.nix
@@ -1,5 +1,10 @@
 { stdenv, fetchurl }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 stdenv.mkDerivation rec {
   name = "patchelf-0.11";
 
diff --git a/pkgs/development/tools/misc/texinfo/common.nix b/pkgs/development/tools/misc/texinfo/common.nix
index 1fb8a6b2f0d..ec51dc2259d 100644
--- a/pkgs/development/tools/misc/texinfo/common.nix
+++ b/pkgs/development/tools/misc/texinfo/common.nix
@@ -6,6 +6,11 @@
 , interactive ? false, ncurses, procps
 }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 let
   crossBuildTools = interactive && stdenv.hostPlatform != stdenv.buildPlatform;
 in
diff --git a/pkgs/development/tools/parsing/bison/default.nix b/pkgs/development/tools/parsing/bison/default.nix
index ba2caac96c9..357c8ea17cf 100644
--- a/pkgs/development/tools/parsing/bison/default.nix
+++ b/pkgs/development/tools/parsing/bison/default.nix
@@ -1,5 +1,10 @@
 { stdenv, fetchurl, m4, perl, help2man }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 stdenv.mkDerivation rec {
   pname = "bison";
   version = "3.6.4";
diff --git a/pkgs/os-specific/linux/kernel/generic.nix b/pkgs/os-specific/linux/kernel/generic.nix
index a9d0cf45168..cab11cc87ae 100644
--- a/pkgs/os-specific/linux/kernel/generic.nix
+++ b/pkgs/os-specific/linux/kernel/generic.nix
@@ -53,6 +53,11 @@
 , ...
 }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 assert stdenv.isLinux;
 
 let
diff --git a/pkgs/os-specific/linux/keyutils/default.nix b/pkgs/os-specific/linux/keyutils/default.nix
index 76869bfde5b..553b0b87f41 100644
--- a/pkgs/os-specific/linux/keyutils/default.nix
+++ b/pkgs/os-specific/linux/keyutils/default.nix
@@ -1,5 +1,10 @@
 { stdenv, fetchurl }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 stdenv.mkDerivation rec {
   pname = "keyutils";
   version = "1.6.1";
diff --git a/pkgs/shells/bash/4.4.nix b/pkgs/shells/bash/4.4.nix
index 4cb3c14a9a0..deeb4093c68 100644
--- a/pkgs/shells/bash/4.4.nix
+++ b/pkgs/shells/bash/4.4.nix
@@ -12,6 +12,11 @@ assert interactive -> readline70 != null;
 assert withDocs -> texinfo != null;
 assert stdenv.hostPlatform.isDarwin -> binutils != null;
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 let
   upstreamPatches = import ./bash-4.4-patches.nix (nr: sha256: fetchurl {
     url = "mirror://gnu/bash/bash-4.4-patches/bash44-${nr}";
diff --git a/pkgs/tools/archivers/gnutar/default.nix b/pkgs/tools/archivers/gnutar/default.nix
index 749f795c449..672c99d80c0 100644
--- a/pkgs/tools/archivers/gnutar/default.nix
+++ b/pkgs/tools/archivers/gnutar/default.nix
@@ -1,5 +1,10 @@
 { stdenv, fetchurl, autoreconfHook, acl }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 stdenv.mkDerivation rec {
   pname = "gnutar";
   version = "1.32";
diff --git a/pkgs/tools/compression/bzip2/default.nix b/pkgs/tools/compression/bzip2/default.nix
index 41dcd54ecdb..3e20258cbbe 100644
--- a/pkgs/tools/compression/bzip2/default.nix
+++ b/pkgs/tools/compression/bzip2/default.nix
@@ -3,6 +3,11 @@
 , autoreconfHook
 }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 stdenv.mkDerivation rec {
   pname = "bzip2";
   version = "1.0.6.0.1";
diff --git a/pkgs/tools/compression/gzip/default.nix b/pkgs/tools/compression/gzip/default.nix
index eb680ff8a06..9628e100c1c 100644
--- a/pkgs/tools/compression/gzip/default.nix
+++ b/pkgs/tools/compression/gzip/default.nix
@@ -4,6 +4,11 @@
 , writeText
 }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 stdenv.mkDerivation rec {
   pname = "gzip";
   version = "1.10";
diff --git a/pkgs/tools/compression/lzip/default.nix b/pkgs/tools/compression/lzip/default.nix
index 62f57a8cca7..e55af8b94ed 100644
--- a/pkgs/tools/compression/lzip/default.nix
+++ b/pkgs/tools/compression/lzip/default.nix
@@ -1,5 +1,10 @@
 { stdenv, fetchurl, texinfo }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 stdenv.mkDerivation rec {
   pname = "lzip";
   version = "1.21";
diff --git a/pkgs/tools/compression/xz/default.nix b/pkgs/tools/compression/xz/default.nix
index 545384c396d..5cf88288d81 100644
--- a/pkgs/tools/compression/xz/default.nix
+++ b/pkgs/tools/compression/xz/default.nix
@@ -1,5 +1,10 @@
 { stdenv, fetchurl, enableStatic ? false }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 stdenv.mkDerivation rec {
   name = "xz-5.2.5";
 
diff --git a/pkgs/tools/misc/coreutils/default.nix b/pkgs/tools/misc/coreutils/default.nix
index 49edc002bec..50d3a2437d7 100644
--- a/pkgs/tools/misc/coreutils/default.nix
+++ b/pkgs/tools/misc/coreutils/default.nix
@@ -10,6 +10,11 @@
 , singleBinary ? "symlinks" # you can also pass "shebangs" or false
 }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 assert aclSupport -> acl != null;
 assert selinuxSupport -> libselinux != null && libsepol != null;
 
diff --git a/pkgs/tools/misc/findutils/default.nix b/pkgs/tools/misc/findutils/default.nix
index 230e401ef82..84dd187e1fc 100644
--- a/pkgs/tools/misc/findutils/default.nix
+++ b/pkgs/tools/misc/findutils/default.nix
@@ -2,6 +2,11 @@
 , coreutils
 }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 stdenv.mkDerivation rec {
   pname = "findutils";
   version = "4.7.0";
diff --git a/pkgs/tools/networking/curl/default.nix b/pkgs/tools/networking/curl/default.nix
index ce24854d04d..9a8a245a790 100644
--- a/pkgs/tools/networking/curl/default.nix
+++ b/pkgs/tools/networking/curl/default.nix
@@ -12,6 +12,11 @@
 , brotliSupport ? false, brotli ? null
 }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 assert http2Support -> nghttp2 != null;
 assert idnSupport -> libidn != null;
 assert ldapSupport -> openldap != null;
diff --git a/pkgs/tools/text/diffutils/default.nix b/pkgs/tools/text/diffutils/default.nix
index 06ecda9ff21..6fd69a9ba4c 100644
--- a/pkgs/tools/text/diffutils/default.nix
+++ b/pkgs/tools/text/diffutils/default.nix
@@ -1,5 +1,10 @@
 { stdenv, fetchurl, xz, coreutils ? null }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 stdenv.mkDerivation rec {
   name = "diffutils-3.7";
 
diff --git a/pkgs/tools/text/gnugrep/default.nix b/pkgs/tools/text/gnugrep/default.nix
index 3f5c4d7d86c..f7e3cd42a9b 100644
--- a/pkgs/tools/text/gnugrep/default.nix
+++ b/pkgs/tools/text/gnugrep/default.nix
@@ -1,5 +1,10 @@
 { stdenv, fetchurl, pcre, libiconv, perl }:
 
+# Note: this package is used for bootstrapping fetchurl, and thus
+# cannot use fetchpatch! All mutable patches (generated by GitHub or
+# cgit) that are needed here should be included directly in Nixpkgs as
+# files.
+
 let version = "3.4"; in
 
 stdenv.mkDerivation {
@@ -19,7 +24,7 @@ stdenv.mkDerivation {
 
   # cygwin: FAIL: multibyte-white-space
   # freebsd: FAIL mb-non-UTF8-performance
-  # all platforms: timing sensitivity in long-pattern-perf 
+  # all platforms: timing sensitivity in long-pattern-perf
   #doCheck = !stdenv.isDarwin && !stdenv.isSunOS && !stdenv.isCygwin && !stdenv.isFreeBSD;
   doCheck = false;