Merging folders and files in terminal overwriting duplicates

Question

I have 2 folders let's call it X and Y, inside them I have several subfolders. I need to merge the content of both, keeping all files and overwriting the duplicates in order to have just Y, with the whole content, no duplicates and without losing any file. I'd like to avoid complex scripts or using cp as I read in many other questions since I want to keep just one folder

my actual tree is

rita/
└── X/
    └── folder1
    └── folder2
    └── foo.txt
└── Y/
    └── folder1
    └── folderA
    └── bar.txt
    └── foo.txt

is

mv /X/ /Y/ 

the right command to use being in rita folder?

i want to obtain this

rita/
└── Y/
    └── folder1
    └── folder2
    └── folderA
    └── bar.txt
    └── foo.txt

or eventually what should I do to get this?

rita/
└── Y/
    └── folder1
    └── folder1 copy
    └── folder2
    └── folderA
    └── bar.txt
    └── foo.txt
    └── foo copy.txt

thanks

Answer 1

According to its manpage, the Unix cp command will overwrite files unless:

• You supply -i (for "Interactive") in which case you will be prompted to overwrite or skip (no "backup copy" option offered)
• You supply -b (for "Backup") in which case it will append ~ to the filename at the end.

To see this in action, I did all this:

$ mkdir temp
$ cd temp
$ touch a.txt
$ touch b.txt
$ mkdir xx
$ ls
a.txt  b.txt  xx
$ cp a.txt b.txt xx
$ ls xx/
a.txt  b.txt
$ cp -i a.txt b.txt xx
cp: overwrite 'xx/a.txt'? n
cp: overwrite 'xx/b.txt'? n
$ cp -b a.txt b.txt xx
$ ls xx/
a.txt  a.txt~  b.txt  b.txt~

_{NOTE: This was done on a Linux machine. Because macOS ships with old binaries, the version supplied with macOS Big Sur & Monterrey (at this time in 2022), doesn't support the -b command. I haven't tested macOS Ventura.}

It Just Works™ (macOS Big Sur & Monterrey)

#Big Sur
$ uname -v
Darwin Kernel Version 20.6.0: Mon Aug 30 06:12:21 PDT 2021; root:xnu-7195.141.6~3/RELEASE_X86_64

#Monterrey
$ uname -v
Darwin Kernel Version 21.6.0: Thu Sep 29 20:13:56 PDT 2022; root:xnu-8020.240.7~1/RELEASE_ARM64_T6000


$ cp -b a.txt b.txt xx
cp: illegal option -- b
usage: cp [-R [-H | -L | -P]] [-fi | -n] [-apvXc] source_file target_file
       cp [-R [-H | -L | -P]] [-fi | -n] [-apvXc] source_file ... target_directory