How do I revert all local changes in Git managed project to previous state?

Look into git-reflog. It will list all the states it remembers (default is 30 days), and you can simply checkout the one you want. For example:

$ git init > /dev/null
$ touch a
$ git add .
$ git commit -m"Add file a" > /dev/null
$ echo 'foo' >> a
$ git commit -a -m"Append foo to a" > /dev/null
$ for i in b c d e; do echo $i >>a; git commit -a -m"Append $i to a" ;done > /dev/null
$ git reset --hard HEAD^^ > /dev/null
$ cat a
foo
b
c
$ git reflog
145c322 HEAD@{0}: HEAD^^: updating HEAD
ae7c2b3 HEAD@{1}: commit: Append e to a
fdf2c5e HEAD@{2}: commit: Append d to a
145c322 HEAD@{3}: commit: Append c to a
363e22a HEAD@{4}: commit: Append b to a
fa26c43 HEAD@{5}: commit: Append foo to a
0a392a5 HEAD@{6}: commit (initial): Add file a
$ git reset --hard HEAD@{2}
HEAD is now at fdf2c5e Append d to a
$ cat a
foo
b
c
d