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170 changes: 20 additions & 150 deletions pro-git/chapter-02/README.md
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# Chapter 2: Git Basics

## Lifecycle of the Status of a File

```mermaid
sequenceDiagram
participant utrack as Untracked
participant umod as Unmodified
participant mod as Modified
participant stage as Staged

utrack->>stage: Add the file
umod->>mod: Edit the file
mod->>stage:Stage the file
umod->>utrack:Remove the file
stage->>umod:Commit
```

## More on the `git status` Command

- `git status`: Show the status of changes as untracked, modified, or staged.

```shell
git status
```

```shell
On branch 2024-10-21_pro-git
Changes not staged for commit:
(use "git add <file>..." to update what will be committed)
(use "git restore <file>..." to discard changes in working directory)
modified: README.md
modified: pro-git/chapter-01/README.md

Untracked files:
(use "git add <file>..." to include in what will be committed)
pro-git/chapter-02/

no changes added to commit (use "git add" and/or "git commit -a")
```

- Shorter `git status`:

```shell
git status --short
```

```shell
M README.md
M pro-git/chapter-01/README.md
?? pro-git/chapter-02/
```

- the first column represents the status of the staging area[^1]
- the second column represents the status of the working directory[^1]

## Ignoring Files

Rules of `.gitignore` files:

- Blank lines or lines starting with `#` are ignored.
- Standard [glob patterns](#glob-patterns) work, and will be applied recursively throughout the entire working directory (e.g. `*.log`).
- You can start patterns with a forward slash (`/`) to avoid recursivity (e.g. `/*.log`).
- You can end patterns with a forward slash (`/`) to specify a directory (e.g. `log/`).
- You can negate a pattern by starting it with an exclamation point (`!`).

### Glob patterns

Glob patterns are regex[^2] for shell environments. Here are some examples:

- `*`: matches zero or more characters
- `[abc]`: matches any of the characters a, b, or c
- `?`: matches a single character
- brackets enclosing characters separated by a hyphen (`-`) represent a range (e.g. `[1-5]` matches any digit from 1 to 5)
- two asterisks (`**`) represent any number of directories (e.g. `a/**/z` matches `a/z`, `a/b/z`, `a/b/c/z`, etc.)

### Example `.gitignore` file[^3]

```gitignore
# ignore all .a files
*.a

# but do track lib.a, even though you're ignoring .a files above
!lib.a

# only ignore the TODO file in the current directory, not subdir/TODO
/TODO

# ignore all files in any directory named build
build/

# ignore doc/notes.txt, but not doc/server/arch.txt
doc/*.txt

# ignore all .pdf file in the doc/ directory and any of its subdirectories
doc/**/*.pdf
```

## Compare Changes Made with `git diff`

Use `git status` as a primer for this:

```shell
git status
```

```shell
On branch 2024-10-21_pro-git
Changes not staged for commit:
(use "git add <file>..." to update what will be committed)
(use "git restore <file>..." to discard changes in working directory)
modified: README.md
modified: pro-git/chapter-01/README.md

Untracked files:
(use "git add <file>..." to include in what will be committed)
pro-git/chapter-02/

no changes added to commit (use "git add" and/or "git commit -a")
```

Let's check what was changed in `README.md`:

```shell
git diff README.md
```

```shell
diff --git a/README.md b/README.md
index 74889a8..b4e04ff 100644
--- a/README.md
+++ b/README.md
@@ -6,4 +6,4 @@ Contains a collection of READMEs for the various areas of my learning. Some exer

- [GNU `grep` and `ripgrep`](gnu-grep/)
- [LDAP](ldap/)
-- [Pro Git](pro-git/)
\ No newline at end of file
+- [Pro Git](pro-git/)
```

## Removing Files from the Staging Area, but Retaining in the Working Directory

```shell
git rm --cached FILENAME
```

This way, the file will no longer be tracked, but you want to retain in the working directory — perhaps to be added to the `.gitignore` file.

[^1]: [See Chapter 01](../chapter-01/README.md) for more information on the staging area and the working directory.
[^2]: Regular expressions
[^3]: [Examples from GitHub](https://github.com/github/gitignore)
## Table of Contents

- [Lifecycle of the Status of a File](lifecycle.md)
- [More on the `git status` Command](status.md)
- [Ignoring Files](ignoring-files.md)
- [Glob Patterns](ignoring-files.md#glob-patterns)
- [Example `.gitignore` file](ignoring-files.md#example-gitignore-file)
- [Compare Changes Made with `git diff`](diff-rm.md#compare-changes-made-with-git-diff)
- [Removing Files from the Staging Area, but Retaining in the Working Directory](diff-rm.md#removing-files-from-the-staging-area-but-retaining-in-the-working-directory)
- [Checking Commit History](commit-history.md#checking-commit-history)
- [`git log`](commit-history.md#git-log)
- [`git log --patch -<n>`](commit-history.md#git-log---patch--n)
- [`git log --stat`](commit-history.md#git-log---stat)
- [`git log --pretty=<option>`](commit-history.md#git-log---prettyoption)
- [Combining the `--pretty` option with the `--graph` option](commit-history.md#combining-the---pretty-option-with-the---graph-option)
- [Common options to `git-log`](commit-history.md#common-options-to-git-log)
- [Limiting Log Output](log-output.md)
- [`git log --since=<n>`](log-output.md#git-log---sincen)
- [`git log -S <string>`](log-output.md#git-log--s-string)
- [Common options to limit output to `git-log`](log-output.md#common-options-to-limit-output-to-git-log)
164 changes: 164 additions & 0 deletions pro-git/chapter-02/commit-history.md
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## Checking Commit History

> [!TIP]
> More options for `git log` can be found here [^1].

### `git log`

Show the commit history:

```shell
commit ca82a6dff817ec66f44342007202690a93763949 (HEAD -> master, origin/master, origin/HEAD)
Author: Scott Chacon <schacon@gmail.com>
Date: Mon Mar 17 21:52:11 2008 -0700

changed the verison number

commit 085bb3bcb608e1e8451d4b2432f8ecbe6306e7e7
Author: Scott Chacon <schacon@gmail.com>
Date: Sat Mar 15 16:40:33 2008 -0700

removed unnecessary test code

commit a11bef06a3f659402fe7563abf99ad00de2209e6
Author: Scott Chacon <schacon@gmail.com>
Date: Sat Mar 15 10:31:28 2008 -0700

first commit
```

### `git log --patch -<n>`

Show the commit history with the diff of each commit (with `<n>` being the last `n` entries to show):

```shell
commit ca82a6dff817ec66f44342007202690a93763949 (HEAD -> master, origin/master, origin/HEAD)
Author: Scott Chacon <schacon@gmail.com>
Date: Mon Mar 17 21:52:11 2008 -0700

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."

commit 085bb3bcb608e1e8451d4b2432f8ecbe6306e7e7
Author: Scott Chacon <schacon@gmail.com>
Date: Sat Mar 15 16:40:33 2008 -0700

removed unnecessary test code

diff --git a/lib/simplegit.rb b/lib/simplegit.rb
index a0a60ae..47c6340 100644
--- a/lib/simplegit.rb
+++ b/lib/simplegit.rb
@@ -18,8 +18,3 @@ class SimpleGit
end

end
-
-if $0 == __FILE__
- git = SimpleGit.new
- puts git.show
-end
```

### `git log --stat`

Show the commit history with the number of insertions and deletions in each commit:

```shell
commit ca82a6dff817ec66f44342007202690a93763949 (HEAD -> master, origin/master, origin/HEAD)
Author: Scott Chacon <schacon@gmail.com>
Date: Mon Mar 17 21:52:11 2008 -0700

changed the verison number

Rakefile | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

commit 085bb3bcb608e1e8451d4b2432f8ecbe6306e7e7
Author: Scott Chacon <schacon@gmail.com>
Date: Sat Mar 15 16:40:33 2008 -0700

removed unnecessary test code

lib/simplegit.rb | 5 -----
1 file changed, 5 deletions(-)

commit a11bef06a3f659402fe7563abf99ad00de2209e6
Author: Scott Chacon <schacon@gmail.com>
Date: Sat Mar 15 10:31:28 2008 -0700

first commit

README | 6 ++++++
Rakefile | 23 +++++++++++++++++++++++
lib/simplegit.rb | 25 +++++++++++++++++++++++++
3 files changed, 54 insertions(+)
```

### `git log --pretty=<option>`

Show the commit history in one line. Options include:

- `oneline`: show the commit hash and the commit message in one line

```shell
git log --pretty=oneline

ca82a6dff817ec66f44342007202690a93763949 (HEAD -> master, origin/master, origin/HEAD) changed the verison number
085bb3bcb608e1e8451d4b2432f8ecbe6306e7e7 removed unnecessary test code
a11bef06a3f659402fe7563abf99ad00de2209e6 first commit
```

- `format:"%h - %an, %ar : %s"`: show the abbreviated commit hash (`%h`), the author name (`%an`), the author date, relative (`%ar`), and the subject (`%s`) of the commit

```shell
git log git log --pretty=format:"%h - %an, %ad : %s"

ca82a6d - Scott Chacon, 7 years ago : changed the verison number
085bb3b - Scott Chacon, 7 years ago : removed unnecessary test code
a11bef0 - Scott Chacon, 7 years ago : first commit
```

## Combining the `--pretty` option with the `--graph` option

Combining both the `--pretty` and `--graph` options will show the commit history in a graph format. Below is an example of the commit history of this repository:

```shell
git log --pretty=format:"%h %s" --graph

* 0931157 2024-10-21: Pro Git Learnings (#3)
* 9540054 Merge branch 'main' into development
|\
| * cbf9b53 First PR for LDAP (#2)
* | ed64291 First PR for `gnu grep` (#1)
|/
* fe49b8b Initial commit
```

### Common options to `git-log`

- `-p` or `--patch`: Show the patch introduced with each commit.
- `--stat`: Show statistics for files modified in each commit.
- `--shortstat`: Show only the changed/insertions/deletions line from the `--stat` option.
- `--name-only`: Show the list of files modified after the commit information.
- `--name-status`: Show the list of files modified after the commit information, indicating the status of the changes.
- `--abbrev-commit`: Show only the first few characters of the SHA-1 checksum instead of all 40.
- `--relative-date`: Display the date in a relative format (e.g. "2 weeks ago") instead of using the full date format.
- `--graph`: Show an ASCII graph of the branch and merge history beside the log output.
- `--pretty`: Show commits in an alternate format. Options include `oneline`, `short`, `full`, `fuller`, `format`, and `email`.
- `--oneline`: Shorthand for `--pretty=oneline --abbrev-commit` used together.

[^1]: [Manual for `git-log`](https://git-scm.com/docs/git-log)
50 changes: 50 additions & 0 deletions pro-git/chapter-02/diff-rm.md
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## Compare Changes Made with `git diff`

Use `git status` as a primer for this:

```shell
git status
```

```shell
On branch 2024-10-21_pro-git
Changes not staged for commit:
(use "git add <file>..." to update what will be committed)
(use "git restore <file>..." to discard changes in working directory)
modified: README.md
modified: pro-git/chapter-01/README.md

Untracked files:
(use "git add <file>..." to include in what will be committed)
pro-git/chapter-02/

no changes added to commit (use "git add" and/or "git commit -a")
```

Let's check what was changed in `README.md`:

```shell
git diff README.md
```

```shell
diff --git a/README.md b/README.md
index 74889a8..b4e04ff 100644
--- a/README.md
+++ b/README.md
@@ -6,4 +6,4 @@ Contains a collection of READMEs for the various areas of my learning. Some exer

- [GNU `grep` and `ripgrep`](gnu-grep/)
- [LDAP](ldap/)
-- [Pro Git](pro-git/)
\ No newline at end of file
+- [Pro Git](pro-git/)
```

## Removing Files from the Staging Area, but Retaining in the Working Directory

```shell
git rm --cached FILENAME
```

This way, the file will no longer be tracked, but you want to retain in the working directory — perhaps to be added to the `.gitignore` file.
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