How can I replace duplicate line prefixes with blanks?

Question

Is it possible to transform:

John Apple Red 3
John Apple Green 5
John Radish White 2
John Radish Red 7
Tom Apple Red 3
Tom Apple Green 5
Tom Radish White 2
Tom Radish Red 7

to:

John Apple Red 3
           Green 5
     Radish White 2
            Red 7
Tom Apple Red 3
          Green 5
    Radish White 2
           Red 7

using Vim?

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I have a large block of configurations (~10k). Each one is something like

Criterion1=1A Criterion2=2A Criterion3=3A... ConfigItem=valA
Criterion1=1A Criterion2=2A Criterion3=3B... ConfigItem=valB
Criterion1=1A Criterion2=2B Criterion3=3C... ConfigItem=valC
Criterion1=1A Criterion2=2B Criterion3=3D... ConfigItem=valD
Criterion1=1B Criterion2=2E Criterion3=3F... ConfigItem=valE

I'm hoping to simplify the presentation to better understand it. Here's an example:

Criterion1=1A Criterion2=2A Criterion3=3A... ConfigItem=valA
                            Criterion3=3B... ConfigItem=valB
              Criterion2=2B Criterion3=3C... ConfigItem=valC
                            Criterion3=3D... ConfigItem=valD
Criterion1=1B Criterion2=2E Criterion3=3F... ConfigItem=valE

The format I've demonstrated above (replacing common repeated prefixes with spaces) would also help make folding work.

Answer 1

I would run the following commands:

:g/^./move 0
:%s/\v^(.*)\ze.*\n\1/\=substitute(submatch(1), '.', ' ', 'g')
:g/^./move 0

1. g/^./move 0 moves the text upside down. Since the logic has to run from bottom to top but substitution only works from top to bottom I first move the buffer upside down.

2. s/\v^(.*)\ze.*\n\1 splits the current line into: the part that is in common with the next line ((.*)) and the part that is not (.*)

   Remark: I use \ze to:

   1. avoid that the pattern eats part of the next line, otherwise the substitution will apply only on one line out of two and
   2. avoid it eats the second part of the line such that we don't need to replace it.

3. substitute(submatch(1), '.', ' ', 'g') replaces every character of the first part by a space

4. g/^./move 0) restores the lines in the right order.