How do I merge one directory into another using Bash?

Question

I'm looking for shell script that merge files from one directory into another.

Sample:

html/
  a/
    b.html
  index.html

html_new/
  a/
    b2.html
    b.html

Usage:

./mergedirs.sh html html_new

Result:

html/
  a/
    b.html
    b2.html
  index.html

html/a/b.html was replaced by html_new/a/b.html
html/a/b2.html was copied from html_new/a/b2.html
html/index.html was kept untouched

Answer 1

cp -RT source/ destination/

All files and directories in source will end up in destination. For example, source/file1 will be copied to destination/file1.

The -T flag stops source/file1 from being copied to destination/source/file1 instead. (Unfortunately, cp on macOS does not support the -T flag.)