Kohei Nozaki's blog 

Assume this:

kyle-no-MacBook:gitprac5 kyle$ ls -l
total 8
-rw-r--r--+ 1 kyle  staff  5  3  9 09:40 hoge.txt
kyle-no-MacBook:gitprac5 kyle$ cat hoge.txt 
hoge
kyle-no-MacBook:gitprac5 kyle$ git status
# On branch master
nothing to commit, working directory clean
kyle-no-MacBook:gitprac5 kyle$ 

Wasting working tree

kyle-no-MacBook:gitprac5 kyle$ echo hoge >> hoge.txt
kyle-no-MacBook:gitprac5 kyle$ echo untracked > untracked.txt
kyle-no-MacBook:gitprac5 kyle$ echo tracked > tracked.txt
kyle-no-MacBook:gitprac5 kyle$ git add tracked.txt
kyle-no-MacBook:gitprac5 kyle$ git status
# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#   new file:   tracked.txt
#
# 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:   hoge.txt
#
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#
#   untracked.txt
kyle-no-MacBook:gitprac5 kyle$ ls -l
total 24
-rw-r--r--+ 1 kyle  staff  10  3  9 09:45 hoge.txt
-rw-r--r--+ 1 kyle  staff   8  3  9 09:45 tracked.txt
-rw-r--r--+ 1 kyle  staff  10  3  9 09:45 untracked.txt
kyle-no-MacBook:gitprac5 kyle$ 

Do it

• These 2 commands will work:

git reset --hard HEAD
git clean -f

• Let's do it:

kyle-no-MacBook:gitprac5 kyle$ git reset --hard HEAD
HEAD is now at 31e0ee6 initial
kyle-no-MacBook:gitprac5 kyle$ ls -l
total 16
-rw-r--r--+ 1 kyle  staff   5  3  9 09:46 hoge.txt
-rw-r--r--+ 1 kyle  staff  10  3  9 09:45 untracked.txt
kyle-no-MacBook:gitprac5 kyle$ git clean -f
Removing untracked.txt
kyle-no-MacBook:gitprac5 kyle$ ls -l
total 8
-rw-r--r--+ 1 kyle  staff  5  3  9 09:46 hoge.txt
kyle-no-MacBook:gitprac5 kyle$ git status
# On branch master
nothing to commit, working directory clean
kyle-no-MacBook:gitprac5 kyle$ 

• When you want to delete directories, you can use “git clean -fd”.

Assume this:

kyle-no-MacBook:gitprac5 kyle$ ls -l
total 8
-rw-r--r--+ 1 kyle  staff  5  3  9 09:27 hoge.txt
kyle-no-MacBook:gitprac5 kyle$ cat hoge.txt 
hoge
kyle-no-MacBook:gitprac5 kyle$ git status
# On branch master
nothing to commit, working directory clean
kyle-no-MacBook:gitprac5 kyle$ 

Delete

Delete from working tree

kyle-no-MacBook:gitprac5 kyle$ rm hoge.txt
kyle-no-MacBook:gitprac5 kyle$ git status
# On branch master
# Changes not staged for commit:
#   (use "git add/rm <file>..." to update what will be committed)
#   (use "git checkout -- <file>..." to discard changes in working directory)
#
#   deleted:    hoge.txt
#
no changes added to commit (use "git add" and/or "git commit -a")
kyle-no-MacBook:gitprac5 kyle$ 

Add deletion to index

kyle-no-MacBook:gitprac5 kyle$ git rm hoge.txt
rm 'hoge.txt'
kyle-no-MacBook:gitprac5 kyle$ git status
# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#   deleted:    hoge.txt
#
kyle-no-MacBook:gitprac5 kyle$

Commit

kyle-no-MacBook:gitprac5 kyle$ git commit -m 'delete'
[master 8793936] delete
 1 file changed, 1 deletion(-)
 delete mode 100644 hoge.txt
kyle-no-MacBook:gitprac5 kyle$ git status
# On branch master
nothing to commit, working directory clean
kyle-no-MacBook:gitprac5 kyle$ ls -l
kyle-no-MacBook:gitprac5 kyle$ 

Move / Rename

kyle-no-MacBook:gitprac5 kyle$ git mv hoge.txt hige.txt
kyle-no-MacBook:gitprac5 kyle$ git status
# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#   renamed:    hoge.txt -> hige.txt
#
kyle-no-MacBook:gitprac5 kyle$ 

• Another identical operation:

kyle-no-MacBook:gitprac5 kyle$ mv hoge.txt hige.txt
kyle-no-MacBook:gitprac5 kyle$ git rm hoge.txt
rm 'hoge.txt'
kyle-no-MacBook:gitprac5 kyle$ git add hige.txt
kyle-no-MacBook:gitprac5 kyle$ git status
# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#   renamed:    hoge.txt -> hige.txt
#
kyle-no-MacBook:gitprac5 kyle$ 

Assume this:

kyle-no-MacBook:gitprac5 kyle$ ls -l
total 8
-rw-r--r--+ 1 kyle  staff  5  3  9 09:04 hoge.txt
kyle-no-MacBook:gitprac5 kyle$ cat hoge.txt
hoge
kyle-no-MacBook:gitprac5 kyle$ git status
# On branch master
nothing to commit, working directory clean
kyle-no-MacBook:gitprac5 kyle$ 

Show unstaged changes

kyle-no-MacBook:gitprac5 kyle$ echo hogehoge >> hoge.txt
kyle-no-MacBook:gitprac5 kyle$ git diff
diff --git a/hoge.txt b/hoge.txt
index 2262de0..1904c09 100644
--- a/hoge.txt
+++ b/hoge.txt
@@ -1 +1,2 @@
 hoge
+hogehoge
kyle-no-MacBook:gitprac5 kyle$ 

Show staged changes

kyle-no-MacBook:gitprac5 kyle$ git add hoge.txt
kyle-no-MacBook:gitprac5 kyle$ git diff --cached
diff --git a/hoge.txt b/hoge.txt
index 2262de0..1904c09 100644
--- a/hoge.txt
+++ b/hoge.txt
@@ -1 +1,2 @@
 hoge
+hogehoge
kyle-no-MacBook:gitprac5 kyle$ 

• There are no unstaged changes now so result of git diff is empty

kyle-no-MacBook:gitprac5 kyle$ git diff
kyle-no-MacBook:gitprac5 kyle$ 

Show both of unstaged and staged changes

Edit hoge.txt again

kyle-no-MacBook:gitprac5 kyle$ echo hogehogehoge >> hoge.txt

Show unstaged changes

kyle-no-MacBook:gitprac5 kyle$ git diff
diff --git a/hoge.txt b/hoge.txt
index 1904c09..9d1d67e 100644
--- a/hoge.txt
+++ b/hoge.txt
@@ -1,2 +1,3 @@
 hoge
 hogehoge
+hogehogehoge

Show staged changes

kyle-no-MacBook:gitprac5 kyle$ git diff --cached
diff --git a/hoge.txt b/hoge.txt
index 2262de0..1904c09 100644
--- a/hoge.txt
+++ b/hoge.txt
@@ -1 +1,2 @@
 hoge
+hogehoge

• This means that an another copy is created when we execute git add.

Show diff between 2 branches

kyle-no-MacBook:hello kyle$ git diff b4 origin/b4
diff --git a/README.md b/README.md
index b8630fa..9c70835 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1 @@
 b4-local1
-CANCEL
kyle-no-MacBook:hello kyle$ 

Statuses

1. untracked
2. unmodified
3. modified
4. staged

untracked

• Newly created file what not connected to the any part of git.
• We use git add to connect these file to git.

unmodified

• Files connected to git but no changes were made yet.

modified

• Files connected to git and modified.
• When we do commit with this kind of resources only, no changes will be made.

staged

• Files connected to git and modified, and declared to commit next time.

Examples of an newly created file

Create a repository

kyle-no-MacBook:gitprac5 kyle$ git init
Initialized empty Git repository in /Users/kyle/tmp/gitprac5/.git/
kyle-no-MacBook:gitprac5 kyle$ 

Create a file

kyle-no-MacBook:gitprac5 kyle$ echo hoge > hoge.txt
kyle-no-MacBook:gitprac5 kyle$ git status
# On branch master
#
# Initial commit
#
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#
#   hoge.txt
nothing added to commit but untracked files present (use "git add" to track)
kyle-no-MacBook:gitprac5 kyle$ 

• Now hoge.txt is untracked.

Add to Index

kyle-no-MacBook:gitprac5 kyle$ git add hoge.txt
kyle-no-MacBook:gitprac5 kyle$ git status
# On branch master
#
# Initial commit
#
# Changes to be committed:
#   (use "git rm --cached <file>..." to unstage)
#
#   new file:   hoge.txt
#
kyle-no-MacBook:gitprac5 kyle$ 

• Now README is staged (?).

Commit

kyle-no-MacBook:gitprac5 kyle$ git commit -m 'initial'
[master (root-commit) ffbe516] initial
 1 file changed, 1 insertion(+)
 create mode 100644 hoge.txt
kyle-no-MacBook:gitprac5 kyle$ git status
# On branch master
nothing to commit, working directory clean
kyle-no-MacBook:gitprac5 kyle$ 

• Now README is unmodified.

Cancel git add to new file

• We can cancel it like this:

kyle-no-MacBook:gitprac5 kyle$ echo README! > README
kyle-no-MacBook:gitprac5 kyle$ git status
# On branch master
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#
#   README
nothing added to commit but untracked files present (use "git add" to track)
kyle-no-MacBook:gitprac5 kyle$ git add README
kyle-no-MacBook:gitprac5 kyle$ git status
# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#   new file:   README
#
kyle-no-MacBook:gitprac5 kyle$ git reset HEAD README
kyle-no-MacBook:gitprac5 kyle$ git status
# On branch master
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#
#   README
nothing added to commit but untracked files present (use "git add" to track)
kyle-no-MacBook:gitprac5 kyle$ 

• Also this deletes all of untracked files:

kyle-no-MacBook:gitprac5 kyle$ git clean -f
Removing README
kyle-no-MacBook:gitprac5 kyle$ ls -l
total 8
-rw-r--r--+ 1 kyle  staff  5  3  9 08:40 hoge.txt
kyle-no-MacBook:gitprac5 kyle$ git status
# On branch master
nothing to commit, working directory clean
kyle-no-MacBook:gitprac5 kyle$ 

Examples of existing file that already tracked by git

kyle-no-MacBook:gitprac5 kyle$ echo hogehoge >> hoge.txt
kyle-no-MacBook:gitprac5 kyle$ 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:   hoge.txt
#
no changes added to commit (use "git add" and/or "git commit -a")
kyle-no-MacBook:gitprac5 kyle$ 

• Now hoge.txt modified but not staged.

kyle-no-MacBook:gitprac5 kyle$ git add hoge.txt
kyle-no-MacBook:gitprac5 kyle$ git status
# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#   modified:   hoge.txt
#
kyle-no-MacBook:gitprac5 kyle$ 

• Now hoge.txt staged.
• Let's take one more modify.

kyle-no-MacBook:gitprac5 kyle$ echo hogehogehoge >> hoge.txt
kyle-no-MacBook:gitprac5 kyle$ git status
# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#   modified:   hoge.txt
#
# 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:   hoge.txt
#
kyle-no-MacBook:gitprac5 kyle$ 

• This means last change (hogehogehoge) will not send by next commit.
• Next commit will send the change (hogehoge) only.
• So when you want to commit (hogehogehoge) next time, you need to execute git add once again.

kyle-no-MacBook:gitprac5 kyle$ git add hoge.txt
kyle-no-MacBook:gitprac5 kyle$ git status
# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#   modified:   hoge.txt
#
kyle-no-MacBook:gitprac5 kyle$ 

References

1. How to sync local git repo with origin/master eliminating all changes - Stack Overflow
2. git reset についてもまとめてみる - murankの日記