$ cat .gitignore
*.[oa]
The first line tells Git to ignore any files ending in “.o” or “.a” — object and archive files that may be the product of building your code.
The second line tells Git to ignore all files whose names end with a tilde (~), which is used by many text editors such as Emacs to mark temporary files.
You may also include a log, tmp, or pid directory; automatically generated documentation; and so on.
Setting up a .gitignore file for your new repository before you get going is generally a good idea so you don’t accidentally commit files that you really don’t want in your Git repository.
The rules for the patterns you can put in the .gitignore file are as follows:
Standard glob patterns work, and will be applied recursively throughout the entire working tree.
You can start patterns with a forward slash (/) to avoid recursivity.
You can end patterns with a forward slash (/) to specify a directory.
You can negate a pattern by starting it with an exclamation point (!).
Glob patterns are like simplified regular expressions that shells use.
An asterisk (*) matches zero or more characters; [abc] matches any character inside the brackets (in this case a, b, or c); a question mark (?) matches a single character; and brackets enclosing characters separated by a hyphen ([0-9]) matches any character between them (in this case 0 through 9).
You can also use two asterisks to match nested directories; a/**/z would match a/z, a/b/z, a/b/c/z, and so on.
Here is another example .gitignore file:
# ignore all .a files
# but do track lib.a, even though you're ignoring .a files above
!lib.a
# only ignore the TODO file in the current directory, not subdir/TODO
/TODO
# ignore all files in any directory named build
build/
# ignore doc/notes.txt, but not doc/server/arch.txt
doc/*.txt
# ignore all .pdf files in the doc/ directory and any of its subdirectories
doc/**/*.pdf
In the simple case, a repository might have a single .gitignore file in its root directory, which applies recursively to the entire repository.
However, it is also possible to have additional .gitignore files in subdirectories.
The rules in these nested .gitignore files apply only to the files under the directory where they are located.
The Linux kernel source repository has 206 .gitignore files.
It is beyond the scope of this book to get into the details of multiple .gitignore files; see man gitignore for the details.
Viewing Your Staged and Unstaged Changes
If the git status command is too vague for you — you want to know exactly what you changed, not just which files were changed — you can use the git diff command.
We’ll cover git diff in more detail later, but you’ll probably use it most often to answer these two questions: What have you changed but not yet staged?
And what have you staged that you are about to commit?
Although git status answers those questions very generally by listing the file names, git diff shows you the exact lines added and removed — the patch, as it were.
Let’s say you edit and stage the README file again and then edit the CONTRIBUTING.md file without staging it.
If you run your git status command, you once again see something like this:
$ git status
On branch master
Your branch is up-to-date with 'origin/master'.
Changes to be committed:
(use "git reset HEAD <file>..." to unstage)
modified: README
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: CONTRIBUTING.md
To see what you’ve changed but not yet staged, type git diff with no other arguments:
$ git diff
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 8ebb991..643e24f 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -65,7 +65,8 @@ branch directly, things can get messy.
Please include a nice description of your changes when you submit your PR;
if we have to read the whole diff to figure out why you're contributing
in the first place, you're less likely to get feedback and have your change
-merged in.
+merged in. Also, split your changes into comprehensive chunks if your patch is
+longer than a dozen lines.
If you are starting to work on a particular area, feel free to submit a PR
that highlights your work in progress (and note in the PR title that it's
That command compares what is in your working directory with what is in your staging area.
The result tells you the changes you’ve made that you haven’t yet staged.
If you want to see what you’ve staged that will go into your next commit, you can use git diff --staged.
This command compares your staged changes to your last commit:
$ git diff --staged
diff --git a/README b/README
new file mode 100644
index 0000000..03902a1
--- /dev/null
+++ b/README
@@ -0,0 +1 @@
+My Project
It’s important to note that git diff by itself doesn’t show all changes made since your last commit — only changes that are still unstaged.
If you’ve staged all of your changes, git diff will give you no output.
For another example, if you stage the CONTRIBUTING.md file and then edit it, you can use git diff to see the changes in the file that are staged and the changes that are unstaged.
If our environment looks like this:
$ git add CONTRIBUTING.md
$ echo '# test line' >> CONTRIBUTING.md
$ git status
On branch master
Your branch is up-to-date with 'origin/master'.
Changes to be committed:
(use "git reset HEAD <file>..." to unstage)
modified: CONTRIBUTING.md
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: CONTRIBUTING.md
Now you can use git diff to see what is still unstaged:
$ git diff
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 643e24f..87f08c8 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -119,3 +119,4 @@ at the
## Starter Projects
See our [projects list](https://github.com/libgit2/libgit2/blob/development/PROJECTS.md).
+# test line
and git diff --cached to see what you’ve staged so far (--staged and --cached are synonyms):
$ git diff --cached
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 8ebb991..643e24f 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -65,7 +65,8 @@ branch directly, things can get messy.
Please include a nice description of your changes when you submit your PR;
if we have to read the whole diff to figure out why you're contributing
in the first place, you're less likely to get feedback and have your change
-merged in.
+merged in. Also, split your changes into comprehensive chunks if your patch is
+longer than a dozen lines.
If you are starting to work on a particular area, feel free to submit a PR
that highlights your work in progress (and note in the PR title that it's
Git Diff in an External Tool
We will continue to use the git diff command in various ways throughout the rest of the book.
There is another way to look at these diffs if you prefer a graphical or external diff viewing program instead.
If you run git difftool instead of git diff, you can view any of these diffs in software like emerge, vimdiff and many more (including commercial products).
Run git difftool --tool-help to see what is available on your system.
Committing Your Changes
Now that your staging area is set up the way you want it, you can commit your changes.
Remember that anything that is still unstaged — any files you have created or modified that you haven’t run git add on since you edited them — won’t go into this commit.
They will stay as modified files on your disk.
In this case, let’s say that the last time you ran git status, you saw that everything was staged, so you’re ready to commit your changes.
The simplest way to commit is to type git commit:
$ git commit
Doing so launches your editor of choice.
# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
# On branch master
# Your branch is up-to-date with 'origin/master'.
# Changes to be committed:
# new file: README
# modified: CONTRIBUTING.md
".git/COMMIT_EDITMSG" 9L, 283C
You can see that the default commit message contains the latest output of the git status command commented out and one empty line on top.
You can remove these comments and type your commit message, or you can leave them there to help you remember what you’re committing.
For an even more explicit reminder of what you’ve modified, you can pass the -v option to git commit.
Doing so also puts the diff of your change in the editor so you can see exactly what changes you’re committing.
When you exit the editor, Git creates your commit with that commit message (with the comments and diff stripped out).
Alternatively, you can type your commit message inline with the commit command by specifying it after a -m flag, like this:
$ git commit -m "Story 182: fix benchmarks for speed"
[master 463dc4f] Story 182: fix benchmarks for speed
2 files changed, 2 insertions(+)
create mode 100644 README
Now you’ve created your first commit!
You can see that the commit has given you some output about itself: which branch you committed to (master), what SHA-1 checksum the commit has (463dc4f), how many files were changed, and statistics about lines added and removed in the commit.
Remember that the commit records the snapshot you set up in your staging area.
Anything you didn’t stage is still sitting there modified; you can do another commit to add it to your history.
Every time you perform a commit, you’re recording a snapshot of your project that you can revert to or compare to later.
Skipping the Staging Area
Although it can be amazingly useful for crafting commits exactly how you want them, the staging area is sometimes a bit more complex than you need in your workflow.
If you want to skip the staging area, Git provides a simple shortcut.
Adding the -a option to the git commit command makes Git automatically stage every file that is already tracked before doing the commit, letting you skip the git add part:
$ git status
On branch master
Your branch is up-to-date with 'origin/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: CONTRIBUTING.md
no changes added to commit (use "git add" and/or "git commit -a")
$ git commit -a -m 'Add new benchmarks'
[master 83e38c7] Add new benchmarks
1 file changed, 5 insertions(+), 0 deletions(-)
Notice how you don’t have to run git add on the CONTRIBUTING.md file in this case before you commit.
That’s because the -a flag includes all changed files.
This is convenient, but be careful; sometimes this flag will cause you to include unwanted changes.
Removing Files
To remove a file from Git, you have to remove it from your tracked files (more accurately, remove it from your staging area) and then commit.
The git rm command does that, and also removes the file from your working directory so you don’t see it as an untracked file the next time around.
If you simply remove the file from your working directory, it shows up under the “Changes not staged for commit” (that is, unstaged) area of your git status output:
$ rm PROJECTS.md
$ git status
On branch master
Your branch is up-to-date with 'origin/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: PROJECTS.md
no changes added to commit (use "git add" and/or "git commit -a")
Then, if you run git rm, it stages the file’s removal:
$ git rm PROJECTS.md
rm 'PROJECTS.md'
$ git status
On branch master
Your branch is up-to-date with 'origin/master'.
Changes to be committed:
(use "git reset HEAD <file>..." to unstage)
deleted: PROJECTS.md
The next time you commit, the file will be gone and no longer tracked.
If you modified the file or had already added it to the staging area, you must force the removal with the -f option.
This is a safety feature to prevent accidental removal of data that hasn’t yet been recorded in a snapshot and that can’t be recovered from Git.
Another useful thing you may want to do is to keep the file in your working tree but remove it from your staging area.
In other words, you may want to keep the file on your hard drive but not have Git track it anymore.
This is particularly useful if you forgot to add something to your .gitignore file and accidentally staged it, like a large log file or a bunch of .a compiled files.
To do this, use the --cached option:
$ git rm --cached README
You can pass files, directories, and file-glob patterns to the git rm command.
That means you can do things such as:
$ git rm log/\*.log
Note the backslash (\) in front of the *.
This is necessary because Git does its own filename expansion in addition to your shell’s filename expansion.
This command removes all files that have the .log extension in the log/ directory.
Or, you can do something like this:
$ git rm \*~
This command removes all files whose names end with a ~.
Moving Files
Unlike many other VCSs, Git doesn’t explicitly track file movement.
If you rename a file in Git, no metadata is stored in Git that tells it you renamed the file.
However, Git is pretty smart about figuring that out after the fact — we’ll deal with detecting file movement a bit later.
Thus it’s a bit confusing that Git has a mv command.
If you want to rename a file in Git, you can run something like:
$ git mv file_from file_to
and it works fine.
In fact, if you run something like this and look at the status, you’ll see that Git considers it a renamed file:
$ git mv README.md README
$ git status
On branch master
Your branch is up-to-date with 'origin/master'.
Changes to be committed:
(use "git reset HEAD <file>..." to unstage)
renamed: README.md -> README
However, this is equivalent to running something like this:
$ mv README.md README
$ git rm README.md
$ git add README
Git figures out that it’s a rename implicitly, so it doesn’t matter if you rename a file that way or with the mv command.
The only real difference is that git mv is one command instead of three — it’s a convenience function.
More importantly, you can use any tool you like to rename a file, and address the add/rm later, before you commit.
