doc/cmd/EnvCommon | 11 +++++++++++

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+Additional common environment variables:
+
+* NO_COLOR -- disable messages colouring (see [cmd/Progress])
+A [Env] REDO_TOP_DIR
+* REDO_TOP_DIR -- do not search for .do above that directory
+                  (it can contain .redo/top as an alternative)
+* REDO_NO_SYNC -- see [cmd/Fsync]
+* REDO_INODE_TRUST -- see [OOD]
+* REDO_MAKE -- see [Jobserver]
+A [Env] REDO_SHELL
+* REDO_SHELL -- path to the shell invoked instead of /bin/sh