> cat(repo_source(pkg, character()))
> cat(repo_source(pkg, "a"))
Source: <a href='https://github.com/r-lib/pkgdown/blob/master/a'><code>a</code></a>

> cat(repo_source(pkg, letters[1:10]))
Source: <a href='https://github.com/r-lib/pkgdown/blob/master/a'><code>a</code></a>, <a href='https://github.com/r-lib/pkgdown/blob/master/b'><code>b</code></a>, <a href='https://github.com/r-lib/pkgdown/blob/master/c'><code>c</code></a>, and 7 more