This document summarizes several common Git commands: - Git merge joins two or more development histories together in either a fast-forward or no fast-forward manner. - Git log displays commit history and allows formatting and filtering options like oneline, decorate, stats, diffs, shortlog, graph and custom formats. - Other commands covered include revert, checkout, reset, cherry-pick, rebase and filtering log output by amount, date, author, message, file, content and range.

1. Presented By:
Md Swawibe Ul Alam
Junior Software Engineer
Nascenia Limited

2. Merge

3. Git Merge
 What it does?
Join two or more development histories/branches
together

7. Git merge is 2 types:
 Fast forward
 No fast forward

8. Example : Fast-Forward Git Merge
 Let us assume that I created a topic
branch named speedup from the
current master. After working on this
branch for a while (three commits,
those white circles),I finally decided
that I am done and then I pushed it to
my own remote. Meanwhile, nothing
else happened in the master branch.

9.  Now if we use git merge using git fast-
forward then my work is landed on
the source tree. Because master has
not been changed since the commit
(gray circle).whole series of the
commits will be linear.
Example : Fast-Forward Git Merge

10. Example : No Fast-Forward Git Merge
 If we use -no-ff option (it stands for no
fast-forward). In this case, the history
looks slightly different (right side),
there is an additional commit (dotted
circle) emphasizing the merge

12. Rebase

22. Git Revert
 This command creates a new commit that undoes
the changes from a previous commit. This command
adds new history to the project (it doesn't modify
existing history)
 Use this to rollback changes you have committed

23. Git checkout
 Use this to checkout a branch or specific commit
 This will rollback any changes you have in your
working copy
 This will NOT make any changes to the history

24. Git reset
 Use this to rollback changes made to the index (eg:
from git add), which will NOT change the history.
 Use this to change what commit a head is pointing
to, which will change the history

25. Cherry Pick
 What git cherry-pick does, basically, is take a
commit from somewhere else, and "play it back"
wherever you are right now. Because this introduces
the same change with a different parent, Git builds a
new commit with a different ID

26. Cherry Pick : Example

27. ❖ If you were at node H in this graph, and you typed git Cherry-pick E you'd
wind up with a copy of commit E—let's call it "E prime" or E'—that
pointed to H as its parent

28. ❖ if you typed something like git cherry-pick C D E

29. Advanced Git Log
Advanced git log can be divided into two parts :
Formating log output
Filtering log output

30. Formating log output
 Formatting shows how each commit is displayed. Available
formats are-
 Oneline
 Decorating
 Diffs
 Shortlog
 Graph
 Custom formatting

31. Oneline
 The --oneline flag condenses each commit to a single
line.
 $ git log --oneline
 output:
0e25143 Merge branch 'feature'
ad8621a Fix a bug in the feature
16b36c6 Add a new feature
23ad9ad Add the initial code base

32. Decorating
 The --decorate flag makes git log display all of the
references (e.g., branches, tags, etc) that point to
each commit.
 $ git log --oneline --decorate
 output:
0e25143 (HEAD, master) Merge branch 'feature'
ad8621a (feature) Fix a bug in the feature
16b36c6 Add a new feature
23ad9ad (tag: v0.9) Add the initial code base

33. Diffs
 The git log command includes many options for displaying diffs with each
commit. Two of the most common options are -
 --stat
 The --stat option displays the number of insertions and deletions to each file altered by
each commit
 $ git log --stat
 output:
 commit f2a238924e89ca1d4947662928218a06d39068c3
Author: John <john@example.com>
Date: Fri Jun 25 17:30:28 2014 -0500
Add a new feature
hello.py | 105 ++++++++++++++++++++++++-----------------
1 file changed, 67 insertion(+), 38 deletions(-)

34. Diffs cont..
 -p
 To see the actual changes introduced by each commit, pass the -p option
to git log
 $ git log --stat -p
 output:
 commit 16b36c697eb2d24302f89aa22d9170dfe609855b
Author: Mary <mary@example.com>
Date: Fri Jun 25 17:31:57 2014 -0500
Fix a bug in the feature
diff --git a/hello.py b/hello.py
index 18ca709..c673b40 100644
--- a/hello.py
+++ b/hello.py
@@ -13,14 +13,14 @@ B
-print("Hello, World!")
+print("Hello, Git!")

35. Shortlog
 The git shortlog command is a special version of git
log intended for creating release announcements.
 It groups each commit by author and displays the
first line of each commit message

36. Shortlog cont..
$ git shortlog
output:
Mary (2):
Fix a bug in the feature
Fix a serious security hole in our framework
John (3):
Add the initial code base
Add a new feature
Merge branch 'feature'

37. Graph
 The --graph option draws an ASCII graph
representing the branch structure of the commit
history
 This is commonly used in conjunction with the --
oneline and --decorate

38. Graph cont..
$ git log --graph --oneline --decorate
output:
* 0e25143 (HEAD, master) Merge branch 'feature'
|
| * 16b36c6 Fix a bug in the new feature
| * 23ad9ad Start a new feature
* | ad8621a Fix a critical security issue
|/
* 400e4b7 Fix typos in the documentation
* 160e224 Add the initial code base

39. Custom formatting
 For all of your other git log formatting needs the --
pretty=format:"<string>" option.
 Display each commit however we want using printf-
style placeholders

40. Custom formatting cont
$ git log --pretty=format:"%cn committed %h on %cd"
output:
John committed 400e4b7 on Fri Jun 24 12:30:04 2014 -0500
John committed 89ab2cf on Thu Jun 23 17:09:42 2014 -0500
Mary committed 180e223 on Wed Jun 22 17:21:19 2014 -0500
John committed f12ca28 on Wed Jun 22 13:50:31 2014 -0500

41. Filtering Log Output
 Filtering shows which commits are included in the
output. Following commands are used for filtering-
 By Amount
 $ git log -3
 By Date
 $ git log --after="2014-7-1"
 $ git log --after="yesterday"
 $ git log --after="2014-7-1" --before="2014-7-4"

42. Filtering Log Output Cont..
 By Author
 $ git log --author="John"
 $ git log --author="John|Mary" //(Mary or John)
 By Message
 $ git log --grep="JRA-224:"
 By File
 git log -- foo.py bar.py
 By Content
 git log -S"Hello, World!"

43. Filtering Log Output Cont..
 By Range
 $ git log master..feature
 $ git log <since>..<until>
 Filtering Merge Commits
 $ git log --no-merges
 $ git log --merges

44. Md Swawibe Ul Alam