And now we've successfully resolved our merge conflict and committed - the result.
+ the result. + +
+ In a nutshell you use git merge to combine another
+ branch context into your current branch. It automatically figures out
+ how to best combine the different snapshots into a new snapshot with the
+ unique work of both.
+
So far we have been committing snapshots of your project and switching
+ between different isolated contexts, but what if we've forgotten how we've
+ got to where we are? Or what if we want to know how one branch differs
+ from another? Git provides a tool that shows you all the commit messages
+ that have lead up to the snapshot you are currently on, which is called
+ git log.
To understand the log command, you have to understand what information
+ is stored when you run the git commit command to store a
+ snapshot. In addition to the manifest of files and commit message and
+ information about the person who committed it, Git also stores the commit
+ that you based this snapshot on. That is, if you clone a project, what was
+ the snapshot that you modified to get to the snapshot that you saved? This
+ is helpful to give context to how the project got to where it is and allows
+ Git to figure out who changed what. If Git has the snapshot you save and
+ the one you based it on, then it can automatically figure out what you
+ changed. The commit that a new commit was based on is called the "parent".
+
To see a chronological list of the parents of any branch, you can run
+ git log when you are in that branch. For example, if we run
+ git log in the Hello World project that we have been working
+ on in this section, we'll see all the commit messages that we've done.
+
+
+$ git log +commit 8d585ea6faf99facd39b55d6f6a3b3f481ad0d3d +Merge: 3cbb6aa 3ac015d +Author: Scott Chacon <schacon@gmail.com> +Date: Fri Jun 4 12:59:47 2010 +0200 + + Merge branch 'fix_readme' + + Conflicts: + README + +commit 3cbb6aae5c0cbd711c098e113ae436801371c95e +Author: Scott Chacon <schacon@gmail.com> +Date: Fri Jun 4 12:58:53 2010 +0200 + + fixed readme title differently + +commit 3ac015da8ade34d4c7ebeffa2053fcac33fb495b +Author: Scott Chacon <schacon@gmail.com> +Date: Fri Jun 4 12:58:36 2010 +0200 + + fixed readme title + +commit 558151a95567ba4181bab5746bc8f34bd87143d6 +Merge: b7ae93b 3467b0a +Author: Scott Chacon <schacon@gmail.com> +Date: Fri Jun 4 12:37:05 2010 +0200 + + Merge branch 'change_class' +... ++ +
To see a more compact version of the same history, we can use the
+ --oneline option.
+$ git log --oneline +8d585ea Merge branch 'fix_readme' +3cbb6aa fixed readme title differently +3ac015d fixed readme title +558151a Merge branch 'change_class' +b7ae93b added from ruby +3467b0a changed the class name +17f4acf first commit ++ +
What this is telling us is that this is the history of the development + of this project. If the commit messages are descriptive, this can inform + us as to what all changes have been applied or have influenced the current + state of the snapshot and thus what is in it.
+ +We can also use it to see when the history was branched and merged with
+ the very helpful --graph option. Here is the same command
+ but with the topology graph turned on:
+$ git log --oneline --graph +* 8d585ea Merge branch 'fix_readme' +|\ +| * 3ac015d fixed readme title +* | 3cbb6aa fixed readme title differently +|/ +* 558151a Merge branch 'change_class' +|\ +| * 3467b0a changed the class name +* | b7ae93b added from ruby +|/ +* 17f4acf first commit ++ +
Now we can more clearly see when effort diverged and then was merged
+ back together. This is very nice for seeing what has happened or what
+ changes are applied, but
+ it is also incredibly useful for managing your branches. Let's create a new
+ branch, do some work in it and then switch back and do some work in our
+ master branch, then see how the log command can help us figure
+ out what is happening on each.
+ In a nutshell you use git log to list out the commit
+ history or list of changes people have made that have lead to the snapshot
+ at the tip of the branch. This allows you to see how the project in that
+ context got to the state that it is currently in.
+