Git Log

The main goal of a version control system is to track changes to your code. This gives you the possibility to navigate history commits, see who made contributions, figure out bugs, and revert changes. Git offers the git log command to exploit all history possibilities.

The git log command is a utility tool to list and filter the project history and search for particular changes.

The git log command has multiple options that can be split into two kinds: formatting how commits are displayed and filtering which commits are displayed.

The output of the git log command is given in reverse chronological order by default. The last commit will be on top of the showed list.

Basic Git log

The git log is a simple command and one of the most used commands of Git.

Every time you want to check the history, you can type the git log command as follows:

$ git log

commit 4b3251c5e09390ede938a57e103afc663ee538d6 (HEAD -> new_branch)
Author: author_name <author_email@pincode.com>
Date:   Mon Oct 14 23:06:14 2019 +0100
    adding more text on file1

commit 6b5548fa8f6f80259cd45d211624843ebb3375ba (tag: v1.0.0, tag: shows, tag: show, master)
Author: author_name <author_email@pincode.com>
Date:   Fri Oct 11 16:36:36 2019 +0100
    first commit

The above command displays the most recent commits and the status of the head. Each commit includes a unique SHA-ID, the date, time, author information, and some additional details.

To scroll on the view opened by git log command, press K for moving up, J for moving down, and the spacebar for scrolling down by a full page.

If you want to exit the git log command view, press the q button. It will quit from the git log command view and back you to the command line.

Git log oneline

The --oneline flag displays the output as one commit per line. It shows only the commit ID and the first line of the commit message.

The command to shows commit history in oneline will run as follows:

$ git log --oneline
4b3251c (HEAD -> new_branch) adding more text on file1
6b5548f (tag: v1.0.0, tag: shows, tag: show, master) first commit

Git log decorate

The --decorate flag displays all the references (branches and tags) that point to each commit

You can combine --decorate flag with other flags like --oneline.

The command to display all references of commits will run as follows:

$ git log --oneline --decorate 
4b3251c (HEAD -> new_branch) adding more text on file1
6b5548f (tag: v1.0.0, tag: shows, tag: show, master) first commit

Git log stat

The --stat flag displays the number of insertions and deletions to each file affected by each commit. It also shows a summary line of the total records that have been modified.

The command will be used as follows:

$ git log --stat 

commit 6b5548fa8f6f80259cd45d211624843ebb3375ba (tag: v1.0.0, tag: shows, tag: show, master)
Author: author_name <author_email@pincode.com>
Date:   Fri Oct 11 16:36:36 2019 +0100
    first commit
 file1.txt | 1 +
 file2.txt | 1 +
 2 files changed, 2 insertions(+)

Git log patch

The --patch or -p flag displays files that have been modified and their changes.

The command to show the changes introduced by each commit will run as follows:

$ git log -p

commit 6b5548fa8f6f80259cd45d211624843ebb3375ba (tag: v1.0.0, tag: shows, tag: show, master)
Author: author_name <author_email@pincode.com>
Date:   Fri Oct 11 16:36:36 2019 +0100

    first commit

diff --git a/file1.txt b/file1.txt
new file mode 100644
index 0000000..3b18e51
--- /dev/null
+++ b/file1.txt
@@ -0,0 +1 @@
+hello world
diff --git a/file2.txt b/file2.txt
new file mode 100644
index 0000000..14c3187
--- /dev/null
+++ b/file2.txt
@@ -0,0 +1 @@
+Git tutorial is awesome

Git log graph

The --graph flag will draw an ASCII representing the commit history's branch structure.

It's common to use --graph option with --oneline and --decorate options to make it easy and beautiful to display a nice representation of the commit history.

The command to display a nice commit history will run as follows:

$ git log --graph --oneline --decorate

To make it very easy to display a nice commit history, you can create an alias to make it very easy to type the last command ever time.

$ git config --global alias.hist 'log --graph --oneline --decorate'

The above command creates an alias hist, which will show a nice presentation of the commit history.

Custom formatting

The pretty=format: option lets you display each commit the way you want using printf-style placeholders.

For example, the %cn, %H placeholders in the command fellow are replaced with the name of the person who made the commit, and the commit hash.

$ git log --pretty=format:"%H commited by %cn"
4b3251c5e09390ede938a57e103afc663ee538d6 commited by author_name 
6b5548fa8f6f80259cd45d211624843ebb3375ba commited by author_name

Filtering the commit history

Git log command offers the possibility to filter the output according to your needs. Many filters can be applied by amount, by date, by author, by content.

Let's see each of these filters in detail.

By amount

The simplest filtering option for the git log command is limiting the number of commits displayed.

You can limit git log output by including the -<n> option. The following example will show only the 4 most recent commits.

$ git log -4

By date

You can use the --after and --before flags to filter the log's output by date. Both options accept different date formats as a parameter.

The following command will list all the commits after "2012-02-26"

$ git log --after="2019-02-26"

You can also pass in relative references like "12 days ago", "1 week ago" and "yesterday":

$ git log --after="12 days ago"

You can also search for commits between two dates. For example, to show all the commits between 2012-09-16 and 2012-10-12, you would type the following command:

$ git log --after="2019-09-16" --before="2019-10-12"

By author

If you want to search for commits created by a particular user, apply the --author flag. It will filter the commits by author name.

The command git log --author="author_name" can take a regular expression and returns the list of commits created by the given user that match the given pattern.

The command to filter by the exact name author run as follows:

$ git log --author="author_name"

By commit message

To filter by commit message, use the --grep flag. It works similar to the --author flag, but it filters by the commit message instead of the author.

For example, you want to search for commits that change the sorting algorithm you and your team are working with.

$ git log --grep ="sort"

The command above displays all the commits that contain the word "sort" in its commit message.

By content

You can also search for commits that add or remove a particular line of source code.

If you want to search for a string, use the -S"" option, and for a regular expression, use the -G"" option.

For example, if you want to know on which commits the string "hello" was added, you would use the following command :

$ git log -S"hello"