Adds additional validation to 'env_vars_from_file'.
Adds additional validation to 'env_vars_from_file'.

The 'env_file' directive and feature precludes the use of the name
'.env' in the path shared with 'docker-config.yml', regardless of
whether or not it is enabled.

This change adds an additional validation to allow the use of this
path provided it is not a file.

Signed-off-by: Thom Linton <9b3bd604c87d8356d20bd34bc726a13fb15760a0@gmail.com>

menglingwei/denverdino.github.io,docker-zh/docker.github.io,jrabbit/compose,LuisBosquez/docker.github.io,joeuo/docker.github.io,dnephin/compose,vdemeester/compose,shin-/docker.github.io,denverdino/compose,rillig/docker.github.io,joaofnfernandes/docker.github.io,alexisbellido/docker.github.io,johnstep/docker.github.io,jrabbit/compose,shin-/compose,joeuo/docker.github.io,joaofnfernandes/docker.github.io,sdurrheimer/compose,thaJeztah/docker.github.io,thaJeztah/compose,shin-/compose,funkyfuture/docker-compose,bdwill/docker.github.io,londoncalling/docker.github.io,joaofnfernandes/docker.github.io,docker-zh/docker.github.io,docker-zh/docker.github.io,phiroict/docker,shubheksha/docker.github.io,aduermael/docker.github.io,jzwlqx/denverdino.github.io,anweiss/docker.github.io,BSWANG/denverdino.github.io,LuisBosquez/docker.github.io,shin-/docker.github.io,LuisBosquez/docker.github.io,aduermael/docker.github.io,swoopla/compose,dbdd4us/compose,alexisbellido/docker.github.io,GM-Alex/compose,menglingwei/denverdino.github.io,denverdino/docker.github.io,hoogenm/compose,thaJeztah/docker.github.io,anweiss/docker.github.io,dnephin/compose,joaofnfernandes/docker.github.io,gdevillele/docker.github.io,johnstep/docker.github.io,alexisbellido/docker.github.io,danix800/docker.github.io,JimGalasyn/docker.github.io,hoogenm/compose,troy0820/docker.github.io,shin-/docker.github.io,docker/docker.github.io,shubheksha/docker.github.io,troy0820/docker.github.io,denverdino/docker.github.io,joeuo/docker.github.io,jzwlqx/denverdino.github.io,alexisbellido/docker.github.io,phiroict/docker,docker/docker.github.io,johnstep/docker.github.io,gdevillele/docker.github.io,JimGalasyn/docker.github.io,rillig/docker.github.io,sdurrheimer/compose,londoncalling/docker.github.io,menglingwei/denverdino.github.io,denverdino/denverdino.github.io,menglingwei/denverdino.github.io,sanscontext/docker.github.io,denverdino/denverdino.github.io,sanscontext/docker.github.io,jzwlqx/denverdino.github.io,sanscontext/docker.github.io,bdwill/docker.github.io,docker-zh/docker.github.io,rillig/docker.github.io,aduermael/docker.github.io,LuisBosquez/docker.github.io,londoncalling/docker.github.io,denverdino/denverdino.github.io,bdwill/docker.github.io,GM-Alex/compose,dbdd4us/compose,thaJeztah/docker.github.io,phiroict/docker,JimGalasyn/docker.github.io,BSWANG/denverdino.github.io,alexisbellido/docker.github.io,danix800/docker.github.io,sanscontext/docker.github.io,johnstep/docker.github.io,joeuo/docker.github.io,BSWANG/denverdino.github.io,jzwlqx/denverdino.github.io,denverdino/denverdino.github.io,anweiss/docker.github.io,funkyfuture/docker-compose,bdwill/docker.github.io,thaJeztah/docker.github.io,vdemeester/compose,gdevillele/docker.github.io,denverdino/docker.github.io,shin-/docker.github.io,aduermael/docker.github.io,phiroict/docker,sanscontext/docker.github.io,joaofnfernandes/docker.github.io,shubheksha/docker.github.io,danix800/docker.github.io,rillig/docker.github.io,phiroict/docker,BSWANG/denverdino.github.io,JimGalasyn/docker.github.io,menglingwei/denverdino.github.io,jzwlqx/denverdino.github.io,gdevillele/docker.github.io,danix800/docker.github.io,michael-k/docker-compose,denverdino/docker.github.io,gdevillele/docker.github.io,swoopla/compose,troy0820/docker.github.io,andrewgee/compose,JimGalasyn/docker.github.io,joeuo/docker.github.io,docker/docker.github.io,denverdino/docker.github.io,anweiss/docker.github.io,londoncalling/docker.github.io,bdwill/docker.github.io,michael-k/docker-compose,londoncalling/docker.github.io,troy0820/docker.github.io,docker-zh/docker.github.io,LuisBosquez/docker.github.io,denverdino/compose,anweiss/docker.github.io,shin-/docker.github.io,shubheksha/docker.github.io,johnstep/docker.github.io,docker/docker.github.io,denverdino/denverdino.github.io,schmunk42/compose,BSWANG/denverdino.github.io,shubheksha/docker.github.io,andrewgee/compose,docker/docker.github.io,schmunk42/compose,thaJeztah/docker.github.io,thaJeztah/compose