C:\Work\gittest>git init
Initialized empty Git repository in C:/Work/gittest/.git/

C:\Work\gittest>echo "bla" > index.html

C:\Work\gittest>git add .

C:\Work\gittest>git status
On branch master

Initial commit

Changes to be committed:
  (use "git rm --cached <file>..." to unstage)

        new file:   index.html


C:\Work\gittest>git commit -m "first commit"
[master (root-commit) b0d1d18] first commit
 1 file changed, 1 insertion(+)
 create mode 100644 index.html

C:\Work\gittest>git checkout -b testbranch
Switched to a new branch 'testbranch'

C:\Work\gittest>echo "foo" > index.html

C:\Work\gittest>git status
On branch testbranch
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

        modified:   index.html

no changes added to commit (use "git add" and/or "git commit -a")

C:\Work\gittest>git checkout master
M       index.html
Switched to branch 'master'

C:\Work\gittest>git status
On branch master
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

        modified:   index.html

no changes added to commit (use "git add" and/or "git commit -a")