project1 hisotory
2
1
2 a.txt   svn message 'best'

project1 hisotory
4
3 a.txt   svn message "after commend"
4 b.txt   svn message "b.text commit"


working file contents + history
Expected outcome (project1 hisotory)

6 b.txt   svn message "b.text commit"
5 a.txt   svn message "after commend"
2 a.txt   svn message "best"

final /svnroot/project1 to project1 history (before revision) + project2 history (after revision) command possible?

/svnroot
    /project1      2
        /branches  1
        /tags      1
        /trunk     2
           a.txt   2

    /project2      4
        /branches  4
        /tags      4
        /trunk     4
           a.txt   3
           b.txt   4


svnadmin dump /svnroot | svndumpfilter include project1 > a.dump
svnadmin dump /svnroot | svndumpfilter include project2 -r 0:4 --incremental > b.dump

svnadmin dump /svnroot2 < a.dump

Please let me know what command you need to do.