reducing redundant lines, partially

"Thierry Blanc [email protected] [sed-users]" <[email protected]> Sun, 20 Nov 2016 19:05:31 +0300
Newsgroups gmane.editors.sed.user
Message-ID <[email protected]>
I have the output of a script in the form

file1/full/path:<number>

file1/full/path:<number>

....

file2/full/path:<number>

I want the output

file1/full/path:<number>:<number> ...file2/full/path:<number>:<number> ...

there might be one or many lines with the same file name.

/home/Journal21/weltsicherheitsrat-uneins.html:9
/home/Journal21/wenig-hoffnung-auf-ein-kriegsende.html:0
/home//Journal21/wenig-hoffnung-auf-ein-kriegsende.html:9
/home/Journal21/wenn-tote-zu-statistiken-werden.html:20





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