When invoked from a shell window, './mach build' works fine; in particular it does not complain about mercurial-setup not having been run. When invoked from Emacs' M-x compile, however... | -*- mode: compilation; default-directory: "~/projects/mozilla/S-mc/" -*- | Compilation started at Sun Sep 6 16:05:48 | | ./mach build | *** MERCURIAL NOT CONFIGURED *** | | mach has detected that you have never run `./mach mercurial-setup`. | | Running this command will ensure your Mercurial version control tool is up | to date and optimally configured for a better, more productive experience | when working on Mozilla projects. | | Please run `./mach mercurial-setup` now. | | Note: `./mach mercurial-setup` does not make any changes without prompting | you first. | | Compilation exited abnormally with code 2 at Sun Sep 6 16:05:48 (N.B. I would appreciate it if there were a --shut-up-and-do-what-I-said-anyway option to override all such complaints.)
You can set I_PREFER_A_SUBOPTIMAL_MERCURIAL_EXPERIENCE=1 in the environment to skip this check, FYI.