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diff --git a/content/blog/git-in-reverse.markdown b/content/blog/git-in-reverse.markdown deleted file mode 100644 index 5971523..0000000 --- a/content/blog/git-in-reverse.markdown +++ /dev/null @@ -1,684 +0,0 @@ ---- -title: "Learning Git in Reverse" -description: "A backwards introduction to the information manager from hell" -tags: - - "Git" - - "Learning" - - "Talks" - - "zData" -date: "2016-01-18" -pubdate: "2016-01-20" -categories: - - "Development" -slug: "git-in-reverse" ---- - -> The content of this post is drafted from contents of a [similarly titled -> presentation][23]. - -It is certainly counter-intuitive to learn to drive by first going backwards, -so why learn how to use Git in reverse? The short answer is: knowing the -internals of Git _should_ make the commands and workflows of Git more -accessible and understandable. - -We will start by touring the plumbing commands and walk all the way through -branching. - -## What is Git± ## - -{{< figure src="http://imgs.xkcd.com/comics/git.png" caption="If that doesn't fix it, git.txt contains the phone number of a friend of mine who understands git. Just wait through a few minutes of 'It's really pretty simple, just think of branches as...' and eventually you'll learn the commands that will fix everything." alt="XKCD on Git" >}} - -Git is a few things to many people, and creating a standard definition is our -first step to fully understanding the nebulous Git. - -Git, developed by Linus Torvalds, is a distributed version control system -(DVCS). This means, Git is a tool for managing, typically, source code and its -related versioning. It accomplishes this by creating a distributed acyclic -graph of the code and folder structure and tracking the changes in the graph. - -Git internally accomplishes this by using a key-value or content addressable -filesystem. Git only knows how to store "objects". There is really no other -_real_ thing that Git is storing. - -## Plumbing ## - -We will start by learning a few of the most basic plumbing commands of Git, -beginning with the [`git-hash-object(1)`][5] command: - -### Git Objects ### - -Git objects are a [zlib][3] compressed binary file stored under the -`.git/objects` folder of any Git repository. They are typically created with -the [`git-hash-object(1)`][5] command are very basic in content: several bytes -of header information used by Git, type and size, and the full contents of the -file Git is storing. - -For the majority of this post, we will be referencing objects created in a -temporary repository: - - $ cd /tmp - $ git init foo - $ cd foo - -> The [`git-init(1)`][4] command creates a new local Git repository in the -> current directory or creates a new directory with a newly initialized Git -> repository. - -After creating a new Git repository, let's examine its current contents: - - ± find .git - .git - .git/objects - .git/objects/info - .git/objects/pack - .git/config - .git/HEAD - .git/hooks - .git/hooks/post-checkout - .git/hooks/post-commit - .git/hooks/ctags - .git/hooks/post-merge - .git/hooks/post-rewrite - .git/refs - .git/refs/tags - .git/refs/heads - -We see that Git has created several folders and files for its internal usage. -We, as developers and users of Git, should generally never need to do anything -to these files, with a small exception for `.git/hooks`. - -As noted before, `.git/objects` will be where Git will store all the objects -(source code and related) we create. `.git/hooks` are used for add custom -operations (white-space, conversions, `ctags`, etc.) to Git's operation. -`.git/refs` is where Git stores information about tags and branches. -`.git/config` is a file for local Git configuration options. This file will -store information about our repository and where it will go for -synchronization. `.git/HEAD` stores a reference to the working copy commit -hash. - -With all this out of the way, we can now start creating objects. - -#### [`git-hash-object(1)`][5] #### - -We can start out by providing some content for [`git-hash-object(1)`][5]: - - ± echo 'foo' | git hash-object --stdin - 257cc5642cb1a054f08cc83f2d943e56fd3ebe99 - -[`git-hash-object(1)`][5] typically expects filenames, so we provide `--stdin` -to tell it we are passing contents from the standard input stream. - -However, since we haven't told Git to store the contents, we have no objects -stored in the `.git/objects` folder. We will need to pass the `-w` flag to -[`git-hash-object(1)`][5] to tell Git to store the contents. - - ± echo 'foo' | git hash-object -w --stdin - 257cc5642cb1a054f08cc83f2d943e56fd3ebe99 - -Now, if we examine the `.git/objects` folder, we will see a new folder and a -new file: - - ± find .git/objects -type f - .git/objects/25/7cc5642cb1a054f08cc83f2d943e56fd3ebe99 - -When Git stores objects, it splits the 40 character hash into two parts: the -first two characters and the last 38. The first two characters, in this case -25, as the folder, and the last 38, `7cc5642cb1a054f08cc83f2d943e56fd3ebe99`, -as the file. The purpose of splitting the hash is to make indexing quicker. -Some of the original motivations for developing Git was a requirement of speed -and performance, can't manage decades of kernel history with a slow tool. - -We can use another Git plumbing command to extract the contents of the object: -`git-cat-file`: - - ± git cat-file -p 257cc5642cb1a054f08cc83f2d943e56fd3ebe99 - foo - -Passing `-p` to `git-cat-file` tells Git to infer the type of the object. -Otherwise, we need to tell Git what the object is. - -Moreover, because we know the objects are zlib compressed, we can use a tool -like `zlib-flate` or similar to peer inside the contents of the files -ourselves: - - ± cat .git/objects/25/7cc5642cb1a054f08cc83f2d943e56fd3ebe99 \ - > | zlib-flate -uncompress - blob 4foo - -Here we see the metadata that Git uses itself, but is otherwise the contents we -expect. - -Perfect. We can store content in Git's object store and we can retrieve the -contents. However, attempting to manage files in this way will be more taxing -than any form of development. Furthermore, we don't have a way to store -filenames yet. Thus, we will need a new type of object, trees. - -### Git Trees ### - -Trees are objects. - -Trees are similarly zlib compressed binaries of the internal data structure of -tracked folder structure of the repository. We create Git trees using the -[`git-update-index(1)`][6] and [`git-write-tree(1)`][7] plumbing commands. - -Since we have an object already added to the Git object store, we can go ahead -and create a basic tree: - - ± git update-index --add --cacheinfo 100644 \ - 257cc5642cb1a054f08cc83f2d943e56fd3ebe99 foo.txt - ± git write-tree - fcf0be4d7e45f0ef9592682ad68e42270b0366b4 - -Thus far, we have created two objects, one to store the contents of `foo.txt` -and another as the tree, which stores binding between the contents and the -filename for `foo.txt`. - -Visually, this may look like something similar to the following image: - -{{< figure src="/media/git-tree-1.png" alt="Git Tree" >}} - -If we inspect the `.git/objects` directory, we should see a new object: - - ± find .git/objects -type f - .git/objects/fc/f0be4d7e45f0ef9592682ad68e42270b0366b4 - .git/objects/25/7cc5642cb1a054f08cc83f2d943e56fd3ebe99 - -As we expected, there is a new folder and new file, `fc` and -`f0be4d7e45f0ef9592682ad68e42270b0366b4`, respectively. - -Since Git trees are actually objects, we can use the `git-cat-file` command -again to print out the contents of the tree: - - ± git cat-file -p fcf0be4d7e45f0ef9592682ad68e42270b0366b4 - 100644 blob 257cc5642cb1a054f08cc83f2d943e56fd3ebe99 foo.txt - -That is, trees are objects where the contents of the object describes a folder -structure "tree". It uses 4 columns for each element of the tree where the -first number uses something similar to the Unix permissions octals; the second -defines the type of object, this can be either `blob` or `tree`; the third is -the hash of the object the entry points to; finally, the last element is the -filename of the object or folder name if the element is a tree. - -A more complicated example of a Git tree may look like the following image: - -{{< figure src="/media/git-tree-2.png" alt="Another Git Tree" >}} - -Now we have file names and the ability to track folders, however, we are still -managing and holding onto the checksums ourselves. Furthermore, we have no -reference to who, when, why, or from where changes are being made. We need -another object to store this information. - -### Git Commits ### - -This will sound familiar: Git commits are ... objects. - -Git stores commits the same way it stores files and trees, as a zlib compressed -binary in the `.git/objects` folders. Similar to trees, the contents of the -object is specifically formatted, but they are stored the same nonetheless. We -can create commits using the [`git-commit-tree(1)`][8] plumbing command. - -The [`git-commit-tree(1)`][8] command takes a message, a tree, and optionally a -parent commit, and creates a commit object. If the parent is not specified, it -creates a root commit. - -We have just created a tree, let's see what committing that tree looks like: - - ± echo 'our first commit' \ - > | git commit-tree fcf0be4d7e45f0ef9592682ad68e42270b0366b4 - d7ee3cdd8bfcc1b8c3f935302f2d2e78e69e4197 - -> Notice, the hash returned here _will_ be different. This hash is dependent on -> time and the author. - -Inspecting our `.git/objects` store, we will see our new object: - - ± find .git/objects -type f - .git/objects/d7/ee3cdd8bfcc1b8c3f935302f2d2e78e69e4197 - .git/objects/fc/f0be4d7e45f0ef9592682ad68e42270b0366b4 - .git/objects/25/7cc5642cb1a054f08cc83f2d943e56fd3ebe99 - -Similar to trees and files, we can use the `git-cat-file` command to inspect -the newly created commit object: - - ± git cat-file -f d7ee3cdd8bfcc1b8c3f935302f2d2e78e69e4197 - tree fcf0be4d7e45f0ef9592682ad68e42270b0366b4 - author kballou <kballou@devnulllabs.io> 1453219069 -0700 - committer kballou <kballou@devnulllabs.io> 1453219069 -0700 - - our first commit - -Breaking down this structure, we have 4 lines, the first line tells which tree -this commit is saving. Since a tree already contains the information of all the -objects that are currently being tracked, the commit only needs to save the -root tree to be able to save _all_ the information for a commit. The second and -third line tell us the author and committer, often these will be the same. They -will be different for GitHub pull requests, or in other situations where the -author of the patch or change is different from the maintainer of the project. -Finally, after a blank line, the rest of the file is reserved for the commit -message; since "our first commit" message is short, it only takes a single -line. - -{{< figure src="/media/git-commit-1.png" alt="Git Commit" >}} - -To inform Git that we have created a commit, we need to add some information to -a few files. First, we need create the `master` reference. We do this by -putting the full commit hash into a file called `.git/refs/heads/master`: - - ± echo d7ee3cdd8bfcc1b8c3f935302f2d2e78e69e4197 > .git/refs/heads/master - -The next thing we should do is update the `.git/HEAD` file to point to our new -reference: - - ± echo 'ref: refs/heads/master' > .git/HEAD - -This brings Git up to speed on everything we have done manually, similarly, -this is what Git does for us when we use the porcelain commands for managing -code. However, it's not really recommended to be manually touching these files, -and in fact, there is another plumbing command for updating these files: -[`git-update-ref(1)`][9]. Instead of the two commands above, we can use a -single invocation of [`git-update-ref(1)`][9] to perform the above: - - ± git update-ref refs/heads/master d7ee3cdd8bfcc1b8c3f935302f2d2e78e69e4197 - -Notice, [`git-update-ref(1)`][9] is an idempotent operation, that is, if the -reference has already been changed to the current hash, running this command -again will yield no change. - -Before we get into the porcelain commands, let's walk through the motions -again: - - ± echo 'bar' > bar.txt - ± git hash-object -w bar.txt - 5716ca5987cbf97d6bb54920bea6adde242d87e6 - ± git update-index --add --cacheinfo 100644 \ - > 5716ca5987cbf97d6bb54920bea6adde242d87e6 bar.txt - ± git write-tree - b98c9a9f9501ddcfcbe02a9de52964ed7dd76d5a - -So far, we have added a new file, `bar.txt` with the contents of `bar`. We have -added the file to a new tree and we have written the tree to the object store. -Before we commit the new tree, let's perform a quick inspection of the tree: - - ± git cat-file -p b98c9a9f9501ddcfcbe02a9de52964ed7dd76d5a - 100644 blob 5716ca5987cbf97d6bb54920bea6adde242d87e6 bar.txt - 100644 blob 257cc5642cb1a054f08cc83f2d943e56fd3ebe99 foo.txt - -An entry for `foo.txt` is present in this new tree. Git is implicitly tracking -previous objects, and carrying them forward, we didn't have to do anything for -Git to do this. Furthermore, the only new objects in the object store so far is -the new object for the contents of `bar.txt` and the object for the new tree: - - ± find .git/objects -type f - .git/objects/b9/8c9a9f9501ddcfcbe02a9de52964ed7dd76d5a - .git/objects/57/16ca5987cbf97d6bb54920bea6adde242d87e6 - .git/objects/d7/ee3cdd8bfcc1b8c3f935302f2d2e78e69e4197 - .git/objects/fc/f0be4d7e45f0ef9592682ad68e42270b0366b4 - .git/objects/25/7cc5642cb1a054f08cc83f2d943e56fd3ebe99 - -Now, we can commit this new tree using the [`git-commit-tree(1)`][8] command: - - ± echo 'our second commit' | git commit-tree \ - > -p d7ee3cdd8bfcc1b8c3f935302f2d2e78e69e4197 \ - > b98c9a9f9501ddcfcbe02a9de52964ed7dd76d5a - b7fd7d75c1375858d8f355735a56228b3eb5e813 - -Let's inspect this newly minted commit: - - ± git cat-file -p b7fd7d75c1375858d8f355735a56228b3eb5e813 - tree b98c9a9f9501ddcfcbe02a9de52964ed7dd76d5a - parent d7ee3cdd8bfcc1b8c3f935302f2d2e78e69e4197 - author kballou <kballou@devnulllabs.io> 1453229013 -0700 - committer kballou <kballou@devnulllabs.io> 1453229013 -0700 - - our second commit - -This commit should look very similar to the previous commit we created. -However, here we have a line dedicated to the "parent" commit, which should -line up with the commit passed to the `-p` flag of [`git-commit-tree(1)`][8]. - -We can update the `master` reference, too, with the new hash: - - ± git update-ref refs/heads/master b7fd7d75c1375858d8f355735a56228b3eb5e813 - -Let's modify `foo.txt` and create another commit: - - ± echo 'foo 2' > foo.txt - ± git hash-object -w foo.txt - a3f555b643cbba18c0e69c82d8820c7487cebe15 - ± git update-index -add --cacheinfo 100644 \ - a3f555b643cbba18c0e69c82d8820c7487cebe15 foo.txt - ± git write-tree - 68b757546e08c1d9033c8802e4de1c0d591d90c8 - ± echo 'our third commit' | git commit-tree \ - > -p b7fd7d75c1375858d8f355735a56228b3eb5e813 \ - > 68b757546e08c1d9033c8802e4de1c0d591d90c8 - 354c7435a9959e662cea02495957daa93d875899 - ± echo 354c7435a9959e662cea02495957daa93d875899 > .git/refs/heads/master - -This final example, we have gone from creating a file, adding the file to a -tree, writing the tree, committing the tree, and finally, pushing forward the -`master` reference. - -There are a few more points to make before we go onto a brief tour of the -porcelain commands. - -Let's go ahead and inspect the current state of the object store: - - ± find .git/objects -type f - .git/objects/35/4c7435a9959e662cea02495957daa93d875899 - .git/objects/68/b757546e08c1d9033c8802e4de1c0d591d90c8 - .git/objects/a3/f555b643cbba18c0e69c82d8820c7487cebe15 - .git/objects/b7/fd7d75c1375858d8f355735a56228b3eb5e813 - .git/objects/57/16ca5987cbf97d6bb54920bea6adde242d87e6 - .git/objects/b9/8c9a9f9501ddcfcbe02a9de52964ed7dd76d5a - .git/objects/d7/ee3cdd8bfcc1b8c3f935302f2d2e78e69e4197 - .git/objects/fc/f0be4d7e45f0ef9592682ad68e42270b0366b4 - .git/objects/25/7cc5642cb1a054f08cc83f2d943e56fd3ebe99 - -There's a few things to notice here, every object we have created so far is -_still_ in the object store, the first version of `foo.txt` is still there -(`257cc5642...`). All the trees are still there, and of course the commits are -still around. This is because Git stores objects. It does not store computed -differences or anything of the sort, it simply stores the objects. Other -version control systems may store the patches, individually version files, -or even track file renames. Git does none of this. Git simply stores only the -objects you ask, it doesn't store the differences between any files, it doesn't -track that a file was renamed. Every commit points to the exact version of -_every_ file at that point in time. If a difference between the working file -and the stored version is asked for, it's computed, if a difference between -yesterday's version of a file and today's, it's computed. If a file was -renamed, it can be inferred by a similarity index and computing the difference -between Git trees. This achieves tremendous performance gains because computing -text differences is relatively cheap compared to attempting to manage code -patches as a means of versioning. - -## Porcelain ## - -Now that we have gone through our tour of the plumbing commands and Git -internals, we can start _actually_ use Git. It will be very rare that the -typical user of Git will ever be using any of the plumbing commands above or -touching files under the `.git` folder in their day-to-day work. For the -day-to-day usage of Git, we will be using the "porcelain" commands, the -commands that take the arduous steps above, and turn them into a pleasant walk -in the park. Essentially, everything we have done above can be accomplished -with two (2) commands in Git: [`git-add(1)`][10] and [`git-commit(1)`][11]. - -Let's initialize a new temporary repository for demonstration: - - $ cd /tmp - $ git init bar - $ cd bar - -After initializing the repository, we can add a file, say, `foo.txt`: - - ± echo 'foo' > foo.txt - -Next, we can use the [`git-add(1)`][10] command to stage the file to be -tracked: - - ± git add foo.txt - -Next, we can use the [`git-commit(1)`][11] command to commit the newly created -`foo.txt` file: - - ± git commit -m 'initial commit' - -Everything we have done so far is now achieved with these two commands. We have -stored the contents of the file, created a tree, and committed the tree. - -There are a few more commands that are very useful to using Git on a regular -basis: [`git-clone(1)`][12], [`git-status(1)`][13], [`git-log(1)`][14], -[`git-pull(1)`][15], [`git-push(1)`][16], and [`git-remote(1)`][17]. - -### [`git-clone(1)`][12] ### - -Before you can contribute to a project, you need your own copy of the -repository, this is where we would use [`git-clone(1)`][12]. As we have seen -before, we can create _new_ repositories with [`git-init(1)`][4], but we still -need a means of getting existing work from another source. - -Here's an example of using `git-clone`: - - $ git clone git://github.com/git/git.git - ... - -There are several protocols that can be used for the when cloning, listed here -in order of preference: - -* `SSH` - - - Bi-directional data transfer - - - Encrypted - - - Typically authenticated, especially without passwords - -* `Git` - - - Pull only - - - Intelligent transfer mechanism - -* `HTTP/S` - - - Bi-directional data transfer - - - Authenticated - - - Unintelligent transfer mechanism - -* `File` - -### [`git-status(1)`][13] ### - -Often, you will need to know the state of the current repository, and the go-to -command to view the current state of the repository is the -[`git-status(1)`][13] command. It will give you information about the currently -modified files, the currently untracked files, the branch you're one, if the -branch is tracked upstream, it will let you know if you have something to push, -etc. - -### [`git-log(1)`][14] ### - -[`git-log(1)`][14] is used to check the history of the repository. Using -[`git-log(1)`][14] with a few arguments, you can get a pretty concise image of -how your projects are changing. - -Some commonly used options you might use might be: - -* `--stat`: Show the files and number of changes for each commit - -* `--oneline`: Show each commit on a single line - -* `--summary`: Show condensed summary of header information - -### [`git-pull(1)`][15] and [`git-fetch(1)`][18] ### - -[`git-pull(1)`][15] is used to pull remote changes into your current working -copy. I prefer not use [`git-pull(1)`][15] because I find it to be slightly -[harmful][19]. Instead, I use either [`git-fetch(1)`][18] or a form of -[`git-remote(1)`][17]. - -[`git-fetch(1)`][18] is a similar command used for "fetching" remote changes, -but does not attempt to automatically merge them into the local branch. - -### [`git-push(1)`][16] ### - -[`git-push(1)`][16] will send your changes to the remote location. By default, -this command will not attempt to overwrite the remote if the changes cannot be -applied with a "fast-forward" merge operation. - -### [`git-remote(1)`][17] ### - -[`git-remote(1)`][17] is an overall "remote" management command. It allows you -to add remotes, rename remotes, and even fetch information about remotes. -"Remotes" are non-local/upstream sources of changes. The remote "origin" is the -default name for the remote of a clone. This could be a co-worker's repository -or it could be the central repository of the project. - -With the [`git-remote(1)`][17] command, we can add a new remote: - - ± git remote add upstream proto://remote - -We can rename a remote: - - ± git remote rename origin upstream - -And my favorite, we can fetch changes from the remote: - - ± git remote update -p origin - -I use this last command so much, in fact, I have created an alias in my -`~/.gitconfig` file: - - [alias] - up = !git remote update -p - -This way, I can decide when and _how_ I want to merge the upstream work into my -local copy. - -The above commands along with `git-add` and `git-commit` will cover the -majority of Git related tasks, as far as simple, non-branching workflows are -concerned. - -For more advanced usage of Git, we can continue to learn about code branching, -git branches, and merging techniques. - -## Branches ## - -Git branches are actually a very simplistic concept in both implementation and -intuition. Code and applications versioned by any version control tool have -their implicit branching points: when one user commits code that another user -isn't yet made aware, the code has diverged from a single path of existence to -multiple paths. This is a form of implicit branching and explicit branching -isn't much different. - -{{< figure src="/media/code-branching.png" alt="Code Branching" >}} - -The structure of Git makes branching trivial, in fact, all that's required is -to create a file that marks the branch point of the code. That is, to create a -file under `.git/refs/heads` that contains the branch's base commit hash. From -there, the code can safely move forward without changing anything of the other -branches. - -{{< figure src="/media/git-branching-1.png" alt="Git Code Branching" >}} - -Branching in Git is accomplished with [`git-branch(1)`][20] and -[`git-checkout(1)`][21]. - -The basic form of [`git-branch(1)`][20] is the following: - - ± git branch {branch_name} [optional branch point] - -If the branch point is not specified, [`git-branch(1)`][20] defaults to the -`HEAD` reference. - -Once the branch is created, you can switch to it using the -[`git-checkout(1)`][21] command: - - ± git checkout {branch_name} - -Moreover, if you're going to be creating a branch and immediately switching to -it, you can use the `-b` flag of [`git-checkout(1)`][21] to do these two steps -in one: - - ± git checkout -b {branch_name} [optional branch point] - -## Merging ## - -Once you're ready to merge your changes from one branch into another branch, -you can use the [`git-merge(1)`][22] command to accomplish that. - -There are a few different ways Git can merge your work between two branches. -The first Git will try is called "fast-forward" merging, where Git will attempt -to play the source branch's commits against the target branch, from the common -history point forward. - -{{< figure src="/media/git-ff-merge-1.png" alt="Git Fast Forward Merge 1" >}} - -{{< figure src="/media/git-ff-merge-2.png" alt="Git Fast Forward Merge 2" >}} - -However, this can only be accomplished if the target branch doesn't have any -changes of its own. - -If the target branch _does_ have changes that are not in the source branch, -Git will attempt to merge the trees and will create a merge commit (assuming -all went well). If a merge conflict arises, the user will need to correct it, -and attempt to re-apply the merge, the resolution of the merge will be in the -merge commit. For more information on merging, see the [`git-merge(1)`][22] -documentation. - -{{< figure src="/media/git-resolve-merge.png" alt="Git parent merge" >}} - -## Summary ## - -Git is not the most complicated version control system out there, and I hope -peering into the internals of Git demonstrates that fact. If anything, it may -seem that Git is very simplistic and unintelligent. But this is actually what -gives Git its power. It's simplistic (recursive) object storage is what gives -Git super powers. Git can infer file renames, branching is trivial, merging is -similarly easier, the storage and tree model are well understood concepts and -the tree and graph algorithms are well studied. - -However, this simplistic approach to storage also has a few problems. Tracking -binary files tends to be expensive because Git isn't storing the difference, -but each version of the file in its entirety. The zlib compression library also -isn't always amazing at compressing binary files either. - -Beyond these problems, Git is a very powerful and capable source control tool. - -### References ### - -[1]: http://git-scm.com/ - -* [Git SCM Site][1] - -[2]: http://git-scm.com/book/en/v2 - -* [Apress: Pro Git][2] - -[3]: https://en.wikipedia.org/wiki/Zlib - -* [zlib compression][3] - -[4]: https://www.kernel.org/pub/software/scm/git/docs/git-init.html - -[5]: https://www.kernel.org/pub/software/scm/git/docs/git-hash-object.html - -[6]: https://www.kernel.org/pub/software/scm/git/docs/git-update-index.html - -[7]: https://www.kernel.org/pub/software/scm/git/docs/git-write-tree.html - -[8]: https://www.kernel.org/pub/software/scm/git/docs/git-commit-tree.html - -[9]: https://www.kernel.org/pub/software/scm/git/docs/git-update-ref.html - -[10]: https://www.kernel.org/pub/software/scm/git/docs/git-add.html - -[11]: https://www.kernel.org/pub/software/scm/git/docs/git-commit.html - -[12]: https://www.kernel.org/pub/software/scm/git/docs/git-clone.html - -[13]: https://www.kernel.org/pub/software/scm/git/docs/git-status.html - -[14]: https://www.kernel.org/pub/software/scm/git/docs/git-log.html - -[15]: https://www.kernel.org/pub/software/scm/git/docs/git-pull.html - -[16]: https://www.kernel.org/pub/software/scm/git/docs/git-push.html - -[17]: https://www.kernel.org/pub/software/scm/git/docs/git-remote.html - -[18]: https://www.kernel.org/pub/software/scm/git/docs/git-fetch.html - -[19]: http://stackoverflow.com/questions/15316601/in-what-cases-could-git-pull-be-harmful#15316602 - -* [SO: Cases `git-pull` could be considered harmful][19] - -[20]: https://www.kernel.org/pub/software/scm/git/docs/git-branch.html - -[21]: https://www.kernel.org/pub/software/scm/git/docs/git-checkout.html - -[22]: https://www.kernel.org/pub/software/scm/git/docs/git-merge.html - -[23]: https://kennyballou.com/git-in-reverse.pdf |