diff --git a/Makefile.in b/Makefile.in
index c5e6c31d2d6..43d3c673222 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -31,7 +31,7 @@ DIST_GARBAGE = config.cache config.log config.status* config-defs.h \
    .mozconfig.mk
 
 ifndef MOZ_PROFILE_USE
-buildid.h: FORCE
+buildid.h source-repo.h: FORCE
 endif
 
 ifdef JS_STANDALONE
@@ -315,12 +315,6 @@ ifdef SOCORRO_SYMBOL_UPLOAD_TOKEN_FILE
 else
 	$(SHELL) $(topsrcdir)/toolkit/crashreporter/tools/upload_symbols.sh $(SYMBOL_INDEX_NAME) '$(DIST)/$(PKG_PATH)$(SYMBOL_FULL_ARCHIVE_BASENAME).zip'
 endif
-
-# MOZ_SOURCE_STAMP is defined in package-name.mk with a deferred assignment.
-# exporting it makes make run its $(shell) command for each invoked submake,
-# so transform it to an immediate assignment.
-MOZ_SOURCE_STAMP := $(MOZ_SOURCE_STAMP)
-export MOZ_SOURCE_STAMP
 endif
 
 .PHONY: update-packaging
diff --git a/b2g/app/Makefile.in b/b2g/app/Makefile.in
index 456034d92bc..6b50b87f72b 100644
--- a/b2g/app/Makefile.in
+++ b/b2g/app/Makefile.in
@@ -2,9 +2,6 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-USE_RCS_MK := 1
-include $(topsrcdir)/config/makefiles/rcs.mk
-
 # Make sure the standalone glue doesn't try to get libxpcom.so from b2g/app.
 NSDISTMODE = copy
 
diff --git a/build/Makefile.in b/build/Makefile.in
index 7b225eb3487..5c8d74f4cb2 100644
--- a/build/Makefile.in
+++ b/build/Makefile.in
@@ -10,19 +10,6 @@ ifdef MOZ_APP_BASENAME
 APP_INI_DEPS = $(topsrcdir)/config/milestone.txt
 
 APP_INI_DEPS += $(DEPTH)/config/autoconf.mk
-
-MOZ_SOURCE_STAMP := $(firstword $(shell cd $(topsrcdir)/$(MOZ_BUILD_APP)/.. && hg parent --template='{node}\n' 2>/dev/null))
-ifdef MOZ_SOURCE_STAMP
-DEFINES += -DMOZ_SOURCE_STAMP='$(MOZ_SOURCE_STAMP)'
-endif
-
-ifdef MOZ_INCLUDE_SOURCE_INFO
-source_repo ?= $(call getSourceRepo,$(topsrcdir)/$(MOZ_BUILD_APP)/..)
-ifneq (,$(source_repo))
-  DEFINES += -DMOZ_SOURCE_REPO='$(source_repo)'
-endif
-endif
-
 endif
 
 # NOTE: Keep .gdbinit in the topsrcdir for people who run gdb from the topsrcdir.
diff --git a/build/application.ini b/build/application.ini
index d09090d3e40..6d27b409730 100644
--- a/build/application.ini
+++ b/build/application.ini
@@ -16,6 +16,7 @@
 #endif
 #filter substitution
 #include @TOPOBJDIR@/buildid.h
+#include @TOPOBJDIR@/source-repo.h
 [App]
 Vendor=@MOZ_APP_VENDOR@
 Name=@MOZ_APP_BASENAME@
diff --git a/build/variables.py b/build/variables.py
index e22de41392c..77ffba0751e 100644
--- a/build/variables.py
+++ b/build/variables.py
@@ -5,6 +5,7 @@
 from __future__ import print_function, unicode_literals
 
 import os
+import subprocess
 import sys
 from datetime import datetime
 
@@ -19,6 +20,53 @@ def buildid_header(output):
     output.write("#define MOZ_BUILDID %s\n" % buildid)
 
 
+def get_program_output(*command):
+    try:
+        with open(os.devnull) as stderr:
+            return subprocess.check_output(command, stderr=stderr)
+    except:
+        return ''
+
+
+def get_hg_info(workdir):
+    repo = get_program_output('hg', '-R', workdir, 'path', 'default')
+    if repo:
+        repo = repo.strip()
+        if repo.startswith('ssh://'):
+            repo = 'https://' + repo[6:]
+        repo = repo.rstrip('/')
+
+    changeset = get_program_output(
+        'hg', '-R', workdir, 'parent', '--template={node}')
+
+    return repo, changeset
+
+
+def source_repo_header(output):
+    # We allow the source repo and changeset to be specified via the
+    # environment (see configure)
+    import buildconfig
+    repo = buildconfig.substs.get('MOZ_SOURCE_REPO')
+    changeset = buildconfig.substs.get('MOZ_SOURCE_CHANGESET')
+    source = ''
+
+    if bool(repo) != bool(changeset):
+        raise Exception('MOZ_SOURCE_REPO and MOZ_SOURCE_CHANGESET both must '
+                        'be set (or not set).')
+
+    if not repo:
+        if os.path.exists(os.path.join(buildconfig.topsrcdir, '.hg')):
+            repo, changeset = get_hg_info(buildconfig.topsrcdir)
+
+    if changeset:
+        output.write('#define MOZ_SOURCE_STAMP %s\n' % changeset)
+
+    if repo and buildconfig.substs.get('MOZ_INCLUDE_SOURCE_INFO'):
+        source = '%s/rev/%s' % (repo, changeset)
+        output.write('#define MOZ_SOURCE_REPO %s\n' % repo)
+        output.write('#define MOZ_SOURCE_URL %s\n' % source)
+
+
 def main(args):
     if (len(args)):
         func = globals().get(args[0])
diff --git a/config/makefiles/makeutils.mk b/config/makefiles/makeutils.mk
index 07961c797c0..95c7791a4b3 100644
--- a/config/makefiles/makeutils.mk
+++ b/config/makefiles/makeutils.mk
@@ -117,9 +117,5 @@ ifdef USE_AUTOTARGETS_MK # mkdir_deps
   include $(topORerr)/config/makefiles/autotargets.mk
 endif
 
-ifdef USE_RCS_MK
-  include $(topORerr)/config/makefiles/rcs.mk
-endif
-
 ## copy(src, dst): recursive copy
 copy_dir = (cd $(1)/. && $(TAR) $(TAR_CREATE_FLAGS) - .) | (cd $(2)/. && tar -xf -)
diff --git a/config/makefiles/rcs.mk b/config/makefiles/rcs.mk
deleted file mode 100644
index b9acada47b3..00000000000
--- a/config/makefiles/rcs.mk
+++ /dev/null
@@ -1,54 +0,0 @@
-# -*- makefile -*-
-# vim:set ts=8 sw=8 sts=8 noet:
-#
-# This Source Code Form is subject to the terms of the Mozilla Public
-# License, v. 2.0. If a copy of the MPL was not distributed with this file,
-# You can obtain one at http://mozilla.org/MPL/2.0/.
-#
-
-ifdef USE_RCS_MK #{
-
-ifndef INCLUDED_RCS_MK #{
-
-MOZ_RCS_TYPE_HG ?= $(notdir $(wildcard $(topsrcdir)/.hg))
-MOZ_RCS_TYPE_GIT ?= $(notdir $(wildcard $(topsrcdir)/.git))
-
-
-###########################################################################
-# HAVE_MERCURIAL_RCS
-###########################################################################
-ifeq (.hg,$(MOZ_RCS_TYPE_HG)) #{
-
-# Intent: Retrieve the http:// repository path for a directory.
-# Usage: $(call getSourceRepo[,repo_dir|args])
-# Args:
-#   path (optional): repository to query.  Defaults to $(topsrcdir)
-getSourceRepo = \
-  $(call FUNC_getSourceRepo,$(if $(1),cd $(1) && hg,hg --repository $(topsrcdir)))
-
-# return: http://hg.mozilla.org/mozilla-central
-FUNC_getSourceRepo = \
-  $(strip \
-    $(patsubst %/,%,\
-    $(patsubst ssh://%,http://%,\
-    $(firstword $(shell $(getargv) showconfig paths.default))\
-    )))
-
-#} HAVE_MERCURIAL_RCS
-
-###########################################################################
-# HAVE_GIT_RCS
-###########################################################################
-else ifeq (.git,$(MOZ_RCS_TYPE_GIT)) #{
-
-GIT ?= git
-getSourceRepo = \
-  $(shell cd $(topsrcdir) && $(GIT) rev-parse --verify HEAD)
-
-endif #} HAVE_GIT_RCS
-
-
-INCLUDED_RCS_MK := 1
-endif #}
-
-endif #}
diff --git a/configure.in b/configure.in
index aedfd392a0c..348cd0a46f7 100644
--- a/configure.in
+++ b/configure.in
@@ -8724,15 +8724,8 @@ fi
 
 # External builds (specifically Ubuntu) may drop the hg repo information, so we allow to
 # explicitly set the repository and changeset information in.
-if test "$MOZILLA_OFFICIAL"; then
-    if test -z "$MOZ_SOURCE_REPO" && test -z "$MOZ_SOURCE_CHANGESET" && test -d ${_topsrcdir}/.hg; then
-        MOZ_SOURCE_CHANGESET=`cd $_topsrcdir && hg parent --template='{node}'`
-        MOZ_SOURCE_REPO=`cd $_topsrcdir && hg showconfig paths.default | sed -e 's|^ssh://|http://|' -e 's|/$||'`
-    fi
-    SOURCE_REV_URL=$MOZ_SOURCE_REPO/rev/$MOZ_SOURCE_CHANGESET
-fi
-AC_SUBST(SOURCE_REV_URL)
-
+AC_SUBST(MOZ_SOURCE_REPO)
+AC_SUBST(MOZ_SOURCE_CHANGESET)
 AC_SUBST(MOZ_INCLUDE_SOURCE_INFO)
 
 if test "$MOZ_TELEMETRY_REPORTING"; then
diff --git a/moz.build b/moz.build
index da220fad781..e2d50c4f66b 100644
--- a/moz.build
+++ b/moz.build
@@ -33,13 +33,16 @@ if not CONFIG['JS_STANDALONE']:
     EXPORTS += [
         '!buildid.h',
         '!mozilla-config.h',
+        '!source-repo.h',
     ]
 
     GENERATED_FILES += [
         'buildid.h',
+        'source-repo.h',
     ]
 
     GENERATED_FILES['buildid.h'].script = 'build/variables.py:buildid_header'
+    GENERATED_FILES['source-repo.h'].script = 'build/variables.py:source_repo_header'
 
     DIRS += [
         'build',
diff --git a/toolkit/components/telemetry/Makefile.in b/toolkit/components/telemetry/Makefile.in
index deea2264c16..52016707ccc 100644
--- a/toolkit/components/telemetry/Makefile.in
+++ b/toolkit/components/telemetry/Makefile.in
@@ -3,9 +3,6 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-USE_RCS_MK := 1
-include $(topsrcdir)/config/makefiles/rcs.mk
-
 include $(topsrcdir)/config/rules.mk
 
 # This is so hacky. Waiting on bug 988938.
diff --git a/toolkit/content/Makefile.in b/toolkit/content/Makefile.in
index e42ed6dc725..0e0e6316dc7 100644
--- a/toolkit/content/Makefile.in
+++ b/toolkit/content/Makefile.in
@@ -3,24 +3,7 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-USE_RCS_MK := 1
-include $(topsrcdir)/config/makefiles/makeutils.mk
-
 DEFINES += \
   -DCXXFLAGS='$(CXXFLAGS)' \
   -DCPPFLAGS='$(CPPFLAGS)' \
   $(NULL)
-
-MOZ_SOURCE_STAMP ?= $(shell hg -R $(topsrcdir) parent --template='{node}\n' 2>/dev/null)
-ifdef MOZ_SOURCE_STAMP
-DEFINES += -DSOURCE_CHANGESET='$(MOZ_SOURCE_STAMP)'
-endif
-
-ifdef MOZ_INCLUDE_SOURCE_INFO
-source_repo ?= $(call getSourceRepo)
-ifneq (,$(filter http%,$(source_repo)))
-  DEFINES += -DSOURCE_REPO='$(source_repo)'
-else ifneq (,$(strip $(source_repo)))
-  DEFINES += -DSOURCE_GIT_COMMIT='$(source_repo)'
-endif
-endif
diff --git a/toolkit/content/buildconfig.html b/toolkit/content/buildconfig.html
index c2480d17886..40f71b850ed 100644
--- a/toolkit/content/buildconfig.html
+++ b/toolkit/content/buildconfig.html
@@ -4,6 +4,7 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 #
 #filter substitution
+#include @TOPOBJDIR@/source-repo.h
 <html>
 <head>
   <meta charset="UTF-8">
@@ -18,14 +19,9 @@
 </head>
 <body class="aboutPageWideContainer">
 <h1>about:buildconfig</h1>
-#ifdef SOURCE_REPO
-#ifdef SOURCE_CHANGESET
+#ifdef MOZ_SOURCE_URL
 <h2>Source</h2>
-<p>Built from <a href="@SOURCE_REPO@/rev/@SOURCE_CHANGESET@">@SOURCE_REPO@/rev/@SOURCE_CHANGESET@</a></p>
-#endif
-#elifdef SOURCE_GIT_COMMIT
-<h2>Source</h2>
-<p>Built from git commit <a href="#">@SOURCE_GIT_COMMIT@</a></p>
+<p>Built from <a href="@MOZ_SOURCE_URL@">@MOZ_SOURCE_URL@</a></p>
 #endif
 <h2>Build platform</h2>
 <table>
diff --git a/toolkit/content/moz.build b/toolkit/content/moz.build
index 0fb97e3e7c3..7d98435b0a4 100644
--- a/toolkit/content/moz.build
+++ b/toolkit/content/moz.build
@@ -31,3 +31,5 @@ with Files('customizeToolbar.*'):
 
 with Files('widgets/*'):
     BUG_COMPONENT = ('Toolkit', 'XUL Widgets')
+
+DEFINES['TOPOBJDIR'] = TOPOBJDIR
diff --git a/toolkit/modules/AppConstants.jsm b/toolkit/modules/AppConstants.jsm
index 5ceb990c6fc..51c33299e49 100644
--- a/toolkit/modules/AppConstants.jsm
+++ b/toolkit/modules/AppConstants.jsm
@@ -1,4 +1,5 @@
 #filter substitution
+#include @TOPOBJDIR@/source-repo.h
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
  * You can obtain one at http://mozilla.org/MPL/2.0/. */
@@ -308,7 +309,10 @@ this.AppConstants = Object.freeze({
   // URL to the hg revision this was built from (e.g.
   // "https://hg.mozilla.org/mozilla-central/rev/6256ec9113c1")
   // On unofficial builds, this is an empty string.
-  SOURCE_REVISION_URL: "@SOURCE_REV_URL@",
+#ifndef MOZ_SOURCE_URL
+#define MOZ_SOURCE_URL
+#endif
+  SOURCE_REVISION_URL: "@MOZ_SOURCE_URL@",
 
   MOZ_NUWA_PROCESS:
 #ifdef MOZ_NUWA_PROCESS
diff --git a/toolkit/modules/moz.build b/toolkit/modules/moz.build
index b8ff635bc2d..349aa292b2f 100644
--- a/toolkit/modules/moz.build
+++ b/toolkit/modules/moz.build
@@ -118,8 +118,7 @@ for var in ('ANDROID_PACKAGE_NAME',
             'MOZ_WIDGET_TOOLKIT',
             'DLL_PREFIX',
             'DLL_SUFFIX',
-            'DEBUG_JS_MODULES',
-            'SOURCE_REV_URL'):
+            'DEBUG_JS_MODULES'):
             DEFINES[var] = CONFIG[var]
 
 for var in ('MOZ_TOOLKIT_SEARCH',
@@ -128,3 +127,5 @@ for var in ('MOZ_TOOLKIT_SEARCH',
             'MOZ_UPDATER'):
     if CONFIG[var]:
         DEFINES[var] = True
+
+DEFINES['TOPOBJDIR'] = TOPOBJDIR
diff --git a/toolkit/mozapps/installer/package-name.mk b/toolkit/mozapps/installer/package-name.mk
index d3f4b194bfe..04d0b3a7c9c 100644
--- a/toolkit/mozapps/installer/package-name.mk
+++ b/toolkit/mozapps/installer/package-name.mk
@@ -156,16 +156,6 @@ ifndef INCLUDED_RCS_MK
   include $(MOZILLA_DIR)/config/makefiles/makeutils.mk
 endif
 
-MOZ_SOURCE_STAMP = $(firstword $(shell hg -R $(MOZILLA_DIR) parent --template="{node}\n" 2>/dev/null))
-
-###########################################################################
-# bug: 746277 - preserve existing functionality.
-# MOZILLA_DIR="": cd $(SPACE); hg # succeeds if ~/.hg exists
-###########################################################################
-ifdef MOZ_INCLUDE_SOURCE_INFO
-MOZ_SOURCE_REPO = $(call getSourceRepo,$(MOZILLA_DIR)$(NULL) $(NULL))
-endif
-
 MOZ_SOURCESTAMP_FILE = $(DIST)/$(PKG_PATH)/$(MOZ_INFO_BASENAME).txt
 MOZ_BUILDINFO_FILE = $(DIST)/$(PKG_PATH)/$(MOZ_INFO_BASENAME).json
 MOZ_MOZINFO_FILE = $(DIST)/$(PKG_PATH)/$(MOZ_INFO_BASENAME).mozinfo.json
diff --git a/toolkit/mozapps/installer/packager.mk b/toolkit/mozapps/installer/packager.mk
index 1b25ca89d04..a35a9495315 100644
--- a/toolkit/mozapps/installer/packager.mk
+++ b/toolkit/mozapps/installer/packager.mk
@@ -96,8 +96,8 @@ GARBAGE += make-package
 make-sourcestamp-file::
 	$(NSINSTALL) -D $(DIST)/$(PKG_PATH)
 	@echo '$(BUILDID)' > $(MOZ_SOURCESTAMP_FILE)
-ifdef MOZ_SOURCE_REPO
-	@echo '$(MOZ_SOURCE_REPO)/rev/$(MOZ_SOURCE_STAMP)' >> $(MOZ_SOURCESTAMP_FILE)
+ifdef MOZ_INCLUDE_SOURCE_INFO
+	@awk '$$2 == "MOZ_SOURCE_URL" {print $$3}' $(DEPTH)/source-repo.h >> $(MOZ_SOURCESTAMP_FILE)
 endif
 
 .PHONY: make-buildinfo-file
@@ -105,8 +105,8 @@ make-buildinfo-file:
 	$(PYTHON) $(MOZILLA_DIR)/toolkit/mozapps/installer/informulate.py \
 		$(MOZ_BUILDINFO_FILE) \
 		BUILDID=$(BUILDID) \
-		$(addprefix MOZ_SOURCE_REPO=,MOZ_SOURCE_REPO=$(MOZ_SOURCE_REPO)) \
-		MOZ_SOURCE_STAMP=$(MOZ_SOURCE_STAMP) \
+		$(addprefix MOZ_SOURCE_REPO=,MOZ_SOURCE_REPO=$(shell awk '$$2 == "MOZ_SOURCE_REPO" {print $$3}' $(DEPTH)/source-repo.h)) \
+		MOZ_SOURCE_STAMP=$(shell awk '$$2 == "MOZ_SOURCE_STAMP" {print $$3}' $(DEPTH)/source-repo.h) \
 		MOZ_PKG_PLATFORM=$(MOZ_PKG_PLATFORM)
 
 .PHONY: make-mozinfo-file
diff --git a/toolkit/mozapps/installer/upload-files.mk b/toolkit/mozapps/installer/upload-files.mk
index 9cfe53c11c3..036fa26a14f 100644
--- a/toolkit/mozapps/installer/upload-files.mk
+++ b/toolkit/mozapps/installer/upload-files.mk
@@ -198,8 +198,8 @@ RPM_CMD = \
   --define 'moz_numeric_app_version $(MOZ_NUMERIC_APP_VERSION)' \
   --define 'moz_rpm_release $(MOZ_RPM_RELEASE)' \
   --define 'buildid $(BUILDID)' \
-  $(if $(MOZ_SOURCE_REPO),--define 'moz_source_repo $(MOZ_SOURCE_REPO)') \
-  --define 'moz_source_stamp $(MOZ_SOURCE_STAMP)' \
+  --define 'moz_source_repo $(shell awk '$$2 == "MOZ_SOURCE_REPO" {print $$3}' $(DEPTH)/source-repo.h)' \
+  --define 'moz_source_stamp $(shell awk '$$2 == "MOZ_SOURCE_STAMP" {print $$3}' $(DEPTH)/source-repo.h)' \
   --define 'moz_branding_directory $(topsrcdir)/$(MOZ_BRANDING_DIRECTORY)' \
   --define '_topdir $(RPMBUILD_TOPDIR)' \
   --define '_rpmdir $(RPMBUILD_RPMDIR)' \
diff --git a/toolkit/xre/Makefile.in b/toolkit/xre/Makefile.in
index 9030fc41fc3..225dc3bbb6e 100644
--- a/toolkit/xre/Makefile.in
+++ b/toolkit/xre/Makefile.in
@@ -5,29 +5,10 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-USE_RCS_MK=1
-include $(topsrcdir)/config/makefiles/makeutils.mk
-
 milestone_txt = $(topsrcdir)/config/milestone.txt
 
 include $(topsrcdir)/config/rules.mk
 
-MOZ_SOURCE_STAMP ?= $(firstword $(shell hg -R $(topsrcdir) parent --template='{node}\n' 2>/dev/null))
-ifneq (,$(strip $(MOZ_SOURCE_STAMP)))
-
-  DEFINES += -DMOZ_SOURCE_STAMP=$(MOZ_SOURCE_STAMP)
-
-  ifdef MOZ_INCLUDE_SOURCE_INFO
-    source_repo := $(call getSourceRepo)
-
-    # extra sanity check for old versions of hg, no showconfig support
-    ifneq (,$(filter http%,$(source_repo)))
-      DEFINES += -DMOZ_SOURCE_REPO=$(source_repo)
-    endif
-  endif
-
-endif # MOZ_SOURCE_STAMP
-
 MOZ_BUILDID   := $(shell awk '{print $$3}' $(DEPTH)/buildid.h)
 $(call errorIfEmpty,GRE_MILESTONE MOZ_BUILDID)
 
diff --git a/toolkit/xre/platform.ini b/toolkit/xre/platform.ini
index 0b337554ab3..01c8b741a1c 100644
--- a/toolkit/xre/platform.ini
+++ b/toolkit/xre/platform.ini
@@ -5,6 +5,7 @@
 #endif
 #filter substitution
 #include @TOPOBJDIR@/buildid.h
+#include @TOPOBJDIR@/source-repo.h
 [Build]
 BuildID=@MOZ_BUILDID@
 Milestone=@GRE_MILESTONE@