Git is one of the most powerful tool in developers' toolbox. If you use it correctly, it dramatically increases productivity of developers and eliminates the waste products continuously. Developers cultivate a development culture on top Git most of the time.
It's powerful but its power is untamed. Many teams fall into several traps of misusing commands and therefore feel uncomfortable while using Git. We mess up Git history, the codebase and the whole preferred branching strategy in seconds. We use branches, merge/rebase strategies, creating commits in wrong ways. Even we never take committing paradigms into account while using Git.
As a software craftsman, I've been using Git for years and I've already educated Git to hundreds of developers in all levels. I'm so lucky; I had a chance to experience huge amount of anti-patterns in time. In this talk, I will talk about what those anti-patterns are and what should we do in order not to fall into them.
4. Are you using git
if all you do is commit-push-pull
use dropbox instead
ANTIPATTERN DANGER
as if it is dropbox ?
5. learn how git works
no worries, I will cover how git behaves
6. the way it keeps
FILES & FOLDERS
working copy
staging area
objects database
repository
the way it keeps
REFERENCES
directed acyclic graph
keeping snapshots
traversing graph
branches, tags, heads
git has 2 mechanisms
12. Object Database
.git Folder / Object Database
Cache
Staging Area / The Index
Remote
Upstream Repo / Remote Repo
Server
Source Code
Working Copy
$ git add .
preparing commits
13. Object Database
.git Folder / Object Database
Cache
Staging Area / The Index
Remote
Upstream Repo / Remote Repo
Server
Source Code
Working Copy
$ git commit -m “initial commit”
commi!ing
14. $ git commit -m “initial commit”
commi!ing
folder
folder
folder
file
file
file
commit
branch
HEAD
For more details, refer to book
Git Internals by Scott Chacon
17. Object Database
.git Folder / Object Database
Cache
Staging Area / The Index
Remote
Upstream Repo / Remote Repo
Server
Source Code
Working Copy
$ git commit -m “initial commit”
commi!ing
18. Object Database
.git Folder / Object Database
Cache
Staging Area / The Index
Remote
Upstream Repo / Remote Repo
Server
Source Code
Working Copy
$ git remote add origin http://upstream.repo
$ git push -u origin master pushing to remote
19. Object Database
.git Folder / Object Database
Cache
Staging Area / The Index
Remote
Upstream Repo / Remote Repo
Server
Source Code
Working Copy
new changes from others are pushed
20. Object Database
.git Folder / Object Database
Cache
Staging Area / The Index
Remote
Upstream Repo / Remote Repo
Server
Source Code
Working Copy
$ git fetch
fetching changes
21. Object Database
.git Folder / Object Database
Cache
Staging Area / The Index
Remote
Upstream Repo / Remote Repo
Server
Source Code
Working Copy
$ git merge FETCHED_HEAD
updating working copy
22. Object Database
.git Folder / Object Database
Cache
Staging Area / The Index
Remote
Upstream Repo / Remote Repo
Server
Source Code
Working Copy
$ git pull
git fetch + git merge
ge!ing changes to source code
23. Object Database
.git Folder / Object Database
Cache
Staging Area / The Index
Remote
Upstream Repo / Remote Repo
Server
Source Code
Working Copy
want to update last commit
24. Object Database
.git Folder / Object Database
Cache
Staging Area / The Index
Remote
Upstream Repo / Remote Repo
Server
Source Code
Working Copy
$ git reset --soft $ git commit --amend/ so" reseting
cannot be reached
27. Object Database
.git Folder / Object Database
Cache
Staging Area / The Index
Remote
Upstream Repo / Remote Repo
Server
Source Code
Working Copy
want to squash or change last commits
28. Object Database
.git Folder / Object Database
Cache
Staging Area / The Index
Remote
Upstream Repo / Remote Repo
Server
Source Code
Working Copy
$ git reset --mixed
mixed reseting
cannot be reached
removed from staging area
29. Object Database
.git Folder / Object Database
Cache
Staging Area / The Index
Remote
Upstream Repo / Remote Repo
Server
Source Code
Working Copy
want to get rid of last commits
30. Object Database
.git Folder / Object Database
Cache
Staging Area / The Index
Remote
Upstream Repo / Remote Repo
Server
Source Code
Working Copy
$ git reset --hard
hard reseting
cannot be reached
removed from staging area
removed from working copy
31. are you brave enough to
jump to any commit ?
jump to a branch
create a branch from a commit
create a branch from a tag
ANTIPATTERN DANGER
$ git checkout feature/PA-121
$ git checkout -b fix/missing-sign-parameter 2449be8
$ git checkout -b hotfix/v1.1 tags/v1
38. merge and unmerge
do you o!en want to
just before releases ?
master
HEAD
TAG/v13
version 14
$ git cherry-pick Every-Single-Commit-We-Want-To-Deploy
43. STEP 0
split your single feature
into mini shippable tasks
master
HEAD
TOPIC
ORIGIN/master
refactorings
tasks, like rest endpoints
testable, deployable
each task will have a
branch, not a feature
44. STEP 1
commit early
commit o!en
no need to compile
no need for CI
it’s only for versioning
do not push
master
HEAD
TOPIC
ORIGIN/master
45. always pull with rebase
$ git pull --rebase origin master
to get forced pushes securely
to rebase your commits
master
HEAD
TOPIC
STEP 2
ORIGIN/master
46. always pull with rebase
$ git pull --rebase origin master
to get forced pushes securely
to rebase your commits
master
HEAD
TOPIC
STEP 2
ORIGIN/master
47. always pull with rebase
$ git pull --rebase origin master
to get forced pushes securely
to rebase your commits
master
HEAD
TOPIC
STEP 2
ORIGIN/master
if you branch is pushed already
$ git push -f
48. always pull with rebase
$ git pull --rebase origin master
to get forced pushes securely
to rebase your commitsmaster
HEAD
TOPIC
STEP 2
ORIGIN/master
if you branch is pushed already
$ git push -f
Sync source branch a!erwards
$ git fetch origin master:master
49. perfect later
make it single commit
$ git reset HEAD~3
or
$ git rebase -i HEAD~3
HEAD
TOPIC
STEP 3
ORIGIN/master
tests are passing
app is working
code is reviewed (*)
master
50. $ git reset HEAD~3 (then commit)
or
$ git rebase -i HEAD~3
HEAD
TOPIC
STEP 3
ORIGIN/master
perfect later
make it single commit
tests are passing
app is working
code is reviewed (*)
master
53. Continuous Integration
validates master branch
continuouslymaster
HEAD
TOPIC
ORIGIN/master
Pull requests can be
used to review code
and to validate before
merging back to master
Scrum tasks are
mapped to commits,
not stories
Github Flow can be
used to govern overall
TAMING
THE POWER OF GIT
make git the king again
Feature flags should be
used whenever possible
Commit early & o"en
perfect later, publish
once philosophy
Deliver frequently
be prepared to send
every single commit
Deleting branches a"er
merge will make your
commit graph readable
55. use terminal
GUIs are prison balls of developers
it’s ok to use GUIs while checking diffs,
resolving conflicts and viewing commit graph
56. do not lose
take extra care while using hard reset
$ git reset --merge HEAD~
Use stash $ git stash save “updates local settings to keep db safe”
$ git reset --hard HEAD~
$ git stash apply stash@{0}
Create a new branch $ git checkout -b feature/PA-121
$ git add settings.xml
$ git commit -m “adds new settings config”
Use hard reset
with merge
and commit into it
uncommited changes
57. TOPIC
HEAD
MASTER
long living branches with care
handle
Squash all commits in your topic branch and
make them available in working copy
$ git merge --squash fix
Squash commit -- not updating HEAD
Automatic merge went well; stopped before committing as requested
$ git add .
$ git commit -m “adds a feature”
$ git branch -D topic
58. long living branches with care
handle
TOPIC
HEAD
MASTER
$ git merge --squash fix
Squash commit -- not updating HEAD
Automatic merge went well; stopped before committing as requested
$ git add .
$ git commit -m “adds a feature”
$ git branch -D topic
Squash all commits in your topic branch and
make them available in working copy
62. messages
are
read!
# WHAT
# <issue id> (this commit will...) <subject>
# WHY and HOW
# Explain why this change is being made
# RELATED
# Provide links or keys to any relevant issues or other resources
# REMEMBER
# use lower case in the subject line
# start with a verb in imperative tone in the subject line
# do not end the subject line with a period
# separate subject from body with a blank line
# use the body to explain what and why vs. how
# can use multiple lines with "-" for bullet points in body
$ git config --global commit.template ~/.git-commit-template.txt
$ git config --global commit.cleanup strip
.git-commit-template.txt
use git commit
templates to
create be"er
commit messages
comtmi
65. master
TAG/v1.1
login
HEAD
DETACHED HEAD STATE
$ git checkout cecd95914
Note: checking out 'cecd95914'.
You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by performing another checkout.
66. master
TAG/v1.1
login
HEAD
DETACHED HEAD STATE
(login)$ git rebase master
First, rewinding head to replay your work on top of it...
Applying: settings
Using index info to reconstruct a base tree...
Falling back to patching base and 3-way merge...
Auto-merging settings
CONFLICT (add/add): Merge conflict in settings
error: Failed to merge in the changes.
Patch failed at 0001 settings
The copy of the patch that failed is found in: .git/rebase-apply/patch
(a16e6e8)$
69. master
TAG/v1.1
login
HEAD
$ git reflog
aa67e3a2c HEAD@{0}: rebase finished: returning to refs/heads/fix/java-sql-Date-violates-LSR
aa67e3a2c HEAD@{1}: rebase: fixes UnsupportedOperationException while calling toIstant() method of java.sql.Date
a45f3c4e5 HEAD@{2}: rebase: checkout develop
630ddad6e HEAD@{3}: checkout: moving from develop to fix/java-sql-Date-violates-LSR
b26cf7a1a HEAD@{4}: rebase: checkout develop
630ddad6e HEAD@{5}: checkout: moving from develop to fix/java-sql-Date-violates-LSR
b26cf7a1a HEAD@{6}: pull: Fast-forward
8b59f8f50 HEAD@{7}: checkout: moving from fix/java-sql-Date-violates-LSR to develop
70. $ git reflog
630ddad6e
the one we are
searching for
master
TAG/v1.1
login
HEAD
aa67e3a2c HEAD@{0}: rebase finished: returning to refs/heads/fix/java-sql-Date-violates-LSR
aa67e3a2c HEAD@{1}: rebase: fixes UnsupportedOperationException while calling toIstant() method of java.sql.Date
a45f3c4e5 HEAD@{2}: rebase: checkout develop
630ddad6e HEAD@{3}: checkout: moving from develop to fix/java-sql-Date-violates-LSR
b26cf7a1a HEAD@{4}: rebase: checkout develop
630ddad6e HEAD@{5}: checkout: moving from develop to fix/java-sql-Date-violates-LSR
b26cf7a1a HEAD@{6}: pull: Fast-forward
8b59f8f50 HEAD@{7}: checkout: moving from fix/java-sql-Date-violates-LSR to develop