As part of our effort to enable Unified Telemetry on Ubuntu, we need the Ubuntu Firefox packagers to define MOZILLA_OFFICIAL when building from a source tree without the VCS info (i.e. no ".hg"/".git" directories). We found that official builds should always have the "build revision" , which seems to be extracted from the hg repo by |getSourceRepo| . This obviously only works when we're in a VCS repository (either git or mercurial), but doesn't/shouldn't if the directory only contains the sources. Surprisingly enough, building doesn't fail when MOZILLA_OFFICIAL is defined and we're building outside of an hg repo.  - https://dxr.mozilla.org/mozilla-central/rev/c5da92c5b4906369dee83629f81d647226ac1038/configure.in#8740  - https://dxr.mozilla.org/mozilla-central/rev/c5da92c5b4906369dee83629f81d647226ac1038/config/makefiles/rcs.mk#26
Created attachment 8711001 [details] about_buildconfig.png I just found that this information seems to be used to show the repository revision the binary was built from (see the attachment). It doesn't get shown on Ubuntu official builds (because they're missing MOZILLA_OFFICIAL and they are build outside of an hg repo). :glandium, do you know if this info is used for something other than about:buildconfig? Would it make sense to allow defining the source revision info through an environment variable when building without .hg/.git?
From investigating for bug 1241111, the build and dependent code work fine with MOZILLA_OFFICIAL / MOZ_INCLUDE_SOURCE_INFO and VCS info missing.
Additionally, bug 1241111 overrides the info shown in about:buildconfig if the VCS info is specified externally.