Allow mounting files/directories as RW instead of always RO

[chrisdruta]

Use Case

Sometimes to speed up batch changes, its useful to use a cache directory (e.g. package manager repository) in-order to avoid hammering package repositories over and over again.

I accomplished this by recompiling the program and removing the ":ro" option for constructing the docker mount commands in run_steps.go which fixed issues I was having.

Security Implications

Looking at previous PR/discussions, I understand this feature was requested to work for remote environments where this ask might add a security risk.

To resolve any potential concerns, maybe only allow local src-cli to mount files in read-write?

Related

• https://github.com/sourcegraph/src-cli/pull/816