live_walkthrough.Rmd

# Git Goat Path for Live Instruction

this is material for the after the [shell intro](https://github.com/UA-Carpentries-Workshops/2019-02-23-WorkshopResources/blob/master/shell-lessons/1_intro-to-shell.md) for feb 2019 workshop

## Intro/Motivation (what)

what we're covering today
fundamental workflow in git
this is what everyone does

analogy = goat path
[goat path pic]
narrow path made on mountain by goats
used daily
short and safe path
very distinct and easy to follow
there because it's safe and well-tested
can be tricky/dangerous to walk off, especially if you don't know the dangers

this is covering goat path git
used by everyone, safe
that's not to say it's easy
everyone has to take time to learn the way

## Intro/Motivation (why)

what do you do when you have a file 
anything (word doc, code, data)
change it and want to save changes
options? 
[jorge cham pic]

this is system to track those changes
instead of multiple files, keep just one copy of each
system tracks all versions of those files
attach message to each version to know what was changed

## Demo

have to first configure git on computer
```{sh}
git config --global user.name "Firstname Lastname"
$ git config --global user.email "firstname.lastname@gmail.com"
```

navigate to GitHub repository folder
repository copied from GitHub
working with data files within that repository
repo = 2019-02-23-WorkshopResources
```{sh}
pwd #/SDC_02-23-2019/repository/data/processed_data
cd ../../..
pwd #/SDC_02-23-2019
cd 2019-02-23-WorkshopResources/shell-lessons/data/gapminder_data/gapminder_by_country/
```

fix a mistake - colleague told us about it
```{sh}
nano Argentina.cc.txt 
# change 1952 to 1954
# save file
```

want to remember that we've made this change
how to do this
goat path
start with git
```{sh}
git status
```
do this command a lot
just tells you what's going on
tells us that we changed a file! 
"Changes not staged for commit"
haven't been staged or commited
will do this next

2 part process
step 1: 
add file to the stage
```{sh}
git add Argentina.cc.txt 
git status
```
check out to see what happened
green text means staged
stage what we have changed

step 2: 
commit staged file
"save" what we have changed
```{sh}
git commit #don't execute
git commit -m #an option that means we leave a message
git commit -m "Fix date error in Argentina file" #include descriptive message of change
```

how do we see our history of changes? 
```{sh}
git status #nothing there has changed since
git log
```
most recent commit (ours) is at top
can see previous commits to this repo
arrow keys to scroll
q to exit

```{sh}
ls
```
there's still only one file! 

let's do it again! 
we're going to make another change to files in this local repo
copy file and change its name
```{sh}
cat Vietnam.cc.txt
```
what's the command for copying? 
what are arguments? 
```{sh}
cp Vietnam.cc.txt Vietnam_copy.cc.txt
```

what does git say? 
```{sh}
git status
```
untracked file
first was modified file bc already committed changes to it before
this is a new file

same process for saving record of change
what is step 1? 
what is step 2? 
```{sh}
git add Vietname_copy.cc.txt
git status
git commit -m "Create copy of Vietnam file"
git status
git log
```

one more time
third time's a charm! 
only interested in data post-2000 for vietname
how do we do this? 
```{sh}
cat Vietnam_copy.cc.txt
tail -2 Vietnam_copy.cc.txt 
tail -2 Vietnam_copy.cc.txt >> Vietnam_recent.cc.txt 
cat Vietnam_recent.cc.txt 
```

save this new version of the file
also keep previous verions
```{sh}
git status
git add Vietname_recent.cc.txt
git commit -m "Subset Vietnam file to post-2000"
git status
git log
```

now we have our files and a record of their changes
trapped on our personal computer
what if we want to share them?
what if we want to save them online? 

[navigate in finder to file]
this is local repository
on personal computer
all we've done is git

can also look at files and versions online
[open up forked repo in browser]
this is the remote repository
they are linked
[click on commits]
the remote repo is out of date
older commits only
none of three new ones

[back to command line]
git command for this
```{sh}
git push
```
[reload page]
there they are! 
click on most recent to look at it
show which file was changed and how

push frequently
at least once a day
or after every commit

foundational workflow of git and github
change files locally
save those changes
update remote repo with changes

there is lot more functionality to git/github (collab)
what we've learned is super useful
[hammer and multitool pics]
learn when you need it, not before
don't be afraid to experiment/do new things
google google google!