Replace .envrc with envrc.repo, allowing the devs to have their own .envrc — heartwood

It’s recommended that developers do this to use envrc.repo:

echo 'source_env envrc.repo' >> .envrc

This is a simpler alternative to rad:z3gqcJUoA1n9HaHKufZs5FCSGazv5/cob/xyz.radicle.patch/f599406e5917dd771c83af3de1a1691eed2206ed

There is a discussion topic on Radicle’s zulip chat related to this: https://radicle.zulipchat.com/#narrow/channel/369277-heartwood/topic/Do.20we.20.2Ahave.2A.20to.20have.20a.20versioned.20.60.2Eenvrc.60.3F/with/590136127

 # Developers that want to use this can add 'source_env envrc.repo' in their .envrc
 if has nix; then
    watch_file rust-toolchain.toml
    use flake
 fi

 /build/artifacts
 /build/*.tar.gz
 /.pre-commit-config.yaml
 /.envrc
 /.direnv/
 /result

 #
 # Install git hooks
 [group('hooks')]
 [group('dev')]
 install-hooks:
     @SUCCESS="{{SUCCESS}}" NORMAL="{{NORMAL}}" scripts/just/install-hooks.sh "{{hook-script}}" "{{hooks}}"

 [group('hooks')]
 check-hooks:
     @HINT="{{HINT}}" NORMAL="{{NORMAL}}" WARN="{{WARN}}" scripts/just/check-hooks.sh "{{hook-script}}" "{{hooks}}"
 # Install default .envrc (append to existing, if there is one)
 [group('dev')]
 install-envrc:
     @SUCCESS="{{SUCCESS}}" NORMAL="{{NORMAL}}" scripts/just/install-default.envrc.sh

     exit 1
 fi
 readonly SENSITIVE_FILES=("justfile" "build.rs" "rust-toolchain.toml")
 SENSITIVE_FILES=("justfile" "build.rs" "rust-toolchain.toml")
 if [ -f ".envrc" ]; then
     SENSITIVE_FILES+=(".envrc.repo")
 fi
 readonly SENSITIVE_FILES
 readonly BASE_BRANCH="master"
 # Check which files were modified compared to the base branch.

 #! /usr/bin/env bash
 set -e
 message="${SUCCESS}.envrc installed${NORMAL}"
 if [ -f .envrc ]; then
     message="${SUCCESS}.envrc updated${NORMAL}"
     sed -i~ -e '/^#:begin:default$/,/^#:end:default$/d' .envrc
 fi
 cat <<_____ >> .envrc
 #:begin:default
 source_env .envrc.repo
 #:end:default
 _____
 echo ""
 echo "${message}"

-	`watch_file rust-toolchain.toml`
-
-	`use flake`