Gitk

Gitk can be a helpful learning utility for those new to version control, or those transitioning from another version control system like subversion. Gitk is a convenience utility that is packaged with Git core. It provides a graphical user interface that helps with visualization of Git's internal mechanics. Other popular Git GUIs are git-gui and Atlassian's own Sourcetree.

Limit commits to a specific file path. To isolate paths from revision names use "--" to separate the paths from any preceding options.

Shows all branches, tags, refs.

Displays the selected item (branches, tags, remotes) as if they were mainline commits. When ＜pattern＞ is passed, further limits refs to ones matching the specified pattern

Render commits older than the specified date.

Sort commits by date.

Show commits that modify conflicted files that were identified during a merge

Renders informative labels that indicate which side of a diff commits are from. Commits from the left side are prefixed with a < symbol and those from the right with a > symbol.

When given a range of commits to display (e.g. commit1..commit2 or commit2 commit1), only display commits that exist directly on the ancestry chain between the commit1 and commit2, i.e. commits that are both descendants of commit1, and ancestors of commit2. (See "History simplification" in git-log(1) for a more detailed explanation.)

Powerful options that let you trace the history of a given code line number range.

In order to provide any valuable output, Gitk needs an underlying repository with committed history. The following code is a sequence of bash commands that will create a new repo with two branches that have commits and have been merged into one.

This demo repository will be a good example to explore with Gitk. This command sequence creates a new repo with 1 commit and an index.txt file. Let us now invoke gitk to examine the repo.

Continuing with our demo repository let us now create an additional commit:

Once the proceeding commands are executed, gitk will need to be reloaded. Either reload gitk from the command line or use the GUI and navigate to File -> Reload. Once reloaded we should see our new commit.

We can see that the main branch ref is now pointed at the new commit. To compare these two commits we use the upper left history panel. Within the history panel click on a commit that will be the base of the diff. Once selected, right click on a second commit to open up a context menu.

This context menu will provide the options of

Selecting either of these options will cause a diff between the two commits to appear in the lower left pane which in our example will look like:

The diff output shows us that index.txt had a new line of "prepended content to index" added between the two commits.

Continuing with our example repo, let's create a new branch.

The proceeding command sequence will create a new branch named new_branch and add file new_branch_file.txt to it. Additionally, new content is added to index.txt and an additional commit is made for that update. We now have a new branch that is 2 commits ahead of main. We must reload Gitk to reflect these changes.

This is a great learning opportunity to discuss Git's branching mechanism. Gitk displays the commits as a straight line sequence of commits. The term branch implies that we should expect a 'branch' or fork in the timeline. Git branches are different from other version control systems. In Git, a branch is a pointer to a commit. The pointer moves to commits as they are created. When you create a git branch, you are not changing anything in the structure of the repository or the source tree. You are just creating a new pointer.

In order to compare the commits that differ between the 2 branches Gitk needs to be launched with a specified revision range. Executing gitk main..new_branch will open Gitk with only the commits between the two branch refs

This is a powerful utility for comparing branches.

Git Gui is another Tcl/Tk based graphical user interface to Git. Whereas Gitk focuses on navigating and visualizing the history of a repository, Git Gui focuses on refining individual commits, single file annotation and does not show project history. Git Gui also supplies menu actions to launch Gitk for history exploration. Git Gui is also invoked from the command line by executing git gui.

In conclusion, Gitk is a graphical interface wrapper for git log. Gitk is incredibly powerful for visualizing and exploring the history of a repository. Gitk is also a helpful tool for learning the internals of Git.