{:check ["true"], :rank ["log" "show" "look"]}

Index

Viewing the Commit History

The general structure of a git repository is as follows:

   0000 *
        |
        |
   a0ef *--
        |  \                 +----------------+
        |   \                |                |
   f13c *    * ceff  ======> | a filesystem   |
        |    |               | of files       |
        |    |               |                |
   89a0 *    * d0d9          +----------------+
        |   /
        |  /
   aa56 *--
    master  dev

In this section, we will be examine how to examine the timeline of a git repository. This will allow us to understand the evolution of the filesystem.

Examining git timelines and their commits
Examine the file directories in a particular commit
Examine the content of a file at a particular version
Understand the differences between two commits

Log

Git Log

git log is a versatile command to examine the timelines and commits of a repository.

Showing the history

\$ git log

commit ca82a6dff817ec66f44342007202690a93763949       # The latest commit $t=2$
Author: Scott Chacon <schacon@gee-mail.com>           #   - author
Date:   Mon Mar 17 21:52:11 2008 -0700                #   - timestamp
                                                      #
    Change version number                             #   - the commit message

commit 085bb3bcb608e1e8451d4b2432f8ecbe6306e7e7       # Previous commit $t=1$
Author: Scott Chacon <schacon@gee-mail.com>
Date:   Sat Mar 15 16:40:33 2008 -0700

    Remove unnecessary test

commit a11bef06a3f659402fe7563abf99ad00de2209e6       # The first commit $t=0$
Author: Scott Chacon <schacon@gee-mail.com>
Date:   Sat Mar 15 10:31:28 2008 -0700

    Initial commit

Commit names are hash codes that are automatically computed.
Commits are listed in the reverse order, with the latest at the top.

Showing recent history with the git log -$n$

\$ git log -2

commit ca82a6dff817ec66f44342007202690a93763949       # The latest commit $t=2$
Author: Scott Chacon <schacon@gee-mail.com>           #   - author
Date:   Mon Mar 17 21:52:11 2008 -0700                #   - timestamp
                                                      #
    Change version number                             #   - the commit message

commit 085bb3bcb608e1e8451d4b2432f8ecbe6306e7e7       # Previous commit $t=1$
Author: Scott Chacon <schacon@gee-mail.com>
Date:   Sat Mar 15 16:40:33 2008 -0700

    Remove unnecessary test

Show history succinctly with the --pretty flag.

\$ git log --pretty=oneline

ca82a6dff817ec66f44342007202690a93763949 Change version number
085bb3bcb608e1e8451d4b2432f8ecbe6306e7e7 Remove unnecessary test
a11bef06a3f659402fe7563abf99ad00de2209e6 Initial commit

lists the commits with limited information
other formats are short, full, and fuller.

Show history with custom format.

\$ git log --pretty=format:"%h - %an, %ar : %s"

ca82a6d - Scott Chacon, 6 years ago : Change version number
085bb3b - Scott Chacon, 6 years ago : Remove unnecessary test
a11bef0 - Scott Chacon, 6 years ago : Initial commit

More documentation available at: https://git-scm.com/docs/pretty-formats

Show timelines as a graph.

\$ git log --pretty=format:"%h %s" --graph

* 2d3acf9 Ignore errors from SIGCHLD on trap
*  5e3ee11 Merge branch 'master' of git://github.com/dustin/grit
|\
| * 420eac9 Add method for getting the current branch
* | 30e367c Timeout code and tests
* | 5a09431 Add timeout protection to grit
* | e1193f8 Support for heads with slashes in them
|/
* d6016bc Require time for xmlschema
*  11d191e Merge branch 'defunkt' into local

The ASCII graph shows multiple branches with branches and merges.
Remember the most recent commits are at the top.

Show

Git show

git show is a command used to show information of a given commit. We will see how to use it to show:

metadata of a commit.
all edits added to the commit.
file content of a particular file

Using git show

Shows the full information of the HEAD:

$ git show
commit ca82a6dff817ec66f443 (HEAD -> master, origin/master, origin/HEAD)  # 
Author: Scott Chacon <schacon@gmail.com>                                  #
Date:   Mon Mar 17 21:52:11 2008 -0700                                    # commit information
                                                                          #
    changed the verison number                                            #

diff --git a/Rakefile b/Rakefile
index a874b73..8f94139 100644
--- a/Rakefile
+++ b/Rakefile
@@ -5,7 +5,7 @@ require 'rake/gempackagetask'
 spec = Gem::Specification.new do |s|
     s.platform  =   Gem::Platform::RUBY
     s.name      =   "simplegit"
-    s.version   =   "0.1.0"
+    s.version   =   "0.1.1"
     s.author    =   "Scott Chacon"
     s.email     =   "schacon@gmail.com"
     s.summary   =   "A simple gem for using Git in Ruby code."

We can specify a commit: git show <commit>

Compact the commit information with --pretty=....

ca82a6dff817ec66f44342007202690a93763949 (HEAD -> master, origin/master, origin/HEAD) changed the verison number
diff --git a/Rakefile b/Rakefile
index a874b73..8f94139 100644
--- a/Rakefile
+++ b/Rakefile
@@ -5,7 +5,7 @@ require 'rake/gempackagetask'
 spec = Gem::Specification.new do |s|
     s.platform  =   Gem::Platform::RUBY
     s.name      =   "simplegit"
-    s.version   =   "0.1.0"
+    s.version   =   "0.1.1"
     s.author    =   "Scott Chacon"
     s.email     =   "schacon@gmail.com"
     s.summary   =   "A simple gem for using Git in Ruby code."

We can specify a commit: git show --pretty=oneline <commit>

Look

Examining files and directories of a commit

Picking a commit

HEAD
HEAD^
HEAD^^
HEAD^^^
HEAD^$n$
Hash code of commits as shown by git log

Listing directory

git ls-tree <commit>
git ls-tree --name-only <commit>

Content of file

git show <commit>:<path>