just-mrrc: support file options for the launcher functionality

When just-mr acts as a launcher, for most subcommand options the
"just args" entry in the rc files provides a convenient way to set
them. However, some options take a file as argument; for those it can
be desirable to set them without assuming a fixed file-system layout
and instead refer to logical roots, in particular the work space.
for the ones that refer to files, it is often desirable to have a potential
reference to the work space. Add this functionality.

1 files changed, 16 insertions, 2 deletions

diff --git a/share/man/just-mrrc.5.md b/share/man/just-mrrc.5.md
index 559c4d5f..85c2ce75 100644
--- a/share/man/just-mrrc.5.md
+++ b/share/man/just-mrrc.5.md
@@ -109,8 +109,8 @@ The just-mrrc is given by a JSON object.
 
  - The value for the key *`"authentication"`* is a JSON object specifying
    client-side authentication options for **`just-mr`**.  
-   For subkey *`"ca cert"`* the value is a single location object the path to
-   a TLS CA certificate.  
+   For subkey *`"ca cert"`* the value is a single location object
+   specifying the path to a TLS CA certificate.
    For subkey *`"client cert"`* the value is a single location object specifying
    the path to a TLS client certificate.  
    For subkey *`"client key"`* the value is a single location object specifying
@@ -118,6 +118,14 @@ The just-mrrc is given by a JSON object.
    Each subkey value can be overwritten by its corresponding command-line
    argument.
 
+ - The value for the key *`"just files"`* is a JSON object. The keys correspond
+   to options that some **`just`** subcommands accept and require a file as
+   argument. For each key, the value is a list of location objects. When
+   **`just-mr`** is used as a launcher and the invoked subcommand is known to
+   support this option, this option is set in the **`just`** invocation with
+   the first matching entry, if any. The supported options are *`"config"`*
+   and *`endpoint-configuration`*.
+
  - The value for the key *`"just args"`* is a JSON object. Its keys are
    **`just`** subcommands and its value is a JSON list of strings. For the
    corresponding subcommand, these strings are prefixed to the **`just`**
@@ -153,6 +161,12 @@ An example just-mrrc file could look like the following:
   , "install": ["--remote-execution-property", "OS:Linux"]
   , "rebuild": ["--remote-execution-property", "OS:Linux"]
   }
+, "just files":
+  { "config":
+    [ {"root": "workspace", "path": "etc/config.json"}
+    , {"root": "home", "path": ".just-config"}
+    ]
+  }
 }
 ```