You can convert these commits to patches, edit the patches manually (substituting old paths with new paths) and then apply.
$ git init
Initialized empty Git repository in /tmp/gitt/.git/
$ mkdir olddir
$ cp /home/vi/code/_/ucontext.cpp olddir/ucontext.cpp
$ git add .
$ git commit -m "initial commit"
[master (root-commit) c0bf371] initial commit
1 files changed, 97 insertions(+), 0 deletions(-)
create mode 100644 olddir/ucontext.cpp
$ printf '22\na\n// Sup, /git/!\n.\nw\nq\n' | ed olddir/ucontext.cpp
1983
if (!stacks) { stacks = stacks3; }
1998
$ git commit -am 'sample commit'
[master 83940c9] sample commit
1 files changed, 1 insertions(+), 0 deletions(-)
$ printf '33\nd\nw\nq\n' | ed olddir/ucontext.cpp
1998
}else{
1990
$ git commit -am 'sample commit 2'
[master 6599932] sample commit 2
1 files changed, 0 insertions(+), 1 deletions(-)
$ git format-patch HEAD~2 --stdout > saved-commites.patch
$ git reset --hard HEAD~2
HEAD is now at c0bf371 initial commit
$ git mv olddir newdir
$ git commit -m 'rename dir'
[master bd8a77e] rename dir
1 files changed, 0 insertions(+), 0 deletions(-)
rename {olddir => newdir}/ucontext.cpp (100%)
$ sed -i.bak 's!\([ab]/\)olddir/!\1newdir/!g' saved-commites.patch
$ git am saved-commites.patch
Applying: sample commit
Applying: sample commit 2