Internal helper used by .write_project_yml(). Replaces the single line
matching placeholder with the lines in replacement, preserving
everything around it. Plain line substitution rather than a YAML round
trip, so the template's explanatory comments survive intact.
Usage
.substitute_block(lines, placeholder, replacement)
Arguments
- lines
Character vector. The template, one element per line.
- placeholder
Character. The placeholder token, matched against the
trimmed line.
- replacement
Character vector. Lines to insert in its place.
Value
A character vector.
