Inspection and Comparison

git log

Description

It is used to view the commit history of a Git repository. It shows a list of commits made to the repository, including details such as commit hash, author, date, and commit message. git log is highly customizable with various options to filter and format the output according to the needs.

Usage

git log [<options>] [<revision range>] [[--] <path>…​]

Options

--oneline: Shows each commit as a single line.

--graph: Displays an ASCII graph of the branch and merge history.

--decorate: Adds branch and tag names to the commit display.

--stat: Shows the file changes (number of insertions and deletions) introduced by each commit.

-p or --patch: Shows the patch (diff) introduced by each commit.

--author=<author>: Filters commits by a specific author.

--since=<date>: Filters commits newer than a specific date.

--until=<date>: Filters commits older than a specific date.

--grep=<pattern>: Filters commits with a commit message that matches the given pattern

-n <number>: Limits the number of commits to show.

git log --oneline
git log --graph
git log --decorate
git log --stat
git log -p
git log --author="Author Name"
git log --since="2023-01-01"
git log --until="2023-12-31"
git log --grep="bug fix"
git log -n 10

What It Does

1. Displays Commit History: Shows a list of commits with details such as commit hash, author, date, and commit message.

2. Filters Commits: Allows filtering commits by author, date, message, and more.

3. Formats Output: Provides various options to format the output, including graphs, pretty print, and custom formats.

Custom Formatting: You can customize the output format using the --pretty=format option. For example:

git log --pretty=format:"%h - %an, %ar : %s"

Filtering: Combining multiple filters (author, date, message) can help you narrow down the commit history to relevant commits.

git log --author="Jane Doe" --since="2023-01-01" --until="2023-12-31" --grep="feature"

File History: Viewing the commit history for a specific file is useful for understanding how a file has evolved over time.

git log path/to/file

Common Use Cases

-- View the Commit History
-- Shows the commit history for the current branch
git log

-- View the Commit History for a Specific File
git log path/to/file

-- View a Graph of the Commit History
-- Displays the commit history as a graph of branches and merges
git log --graph

-- Pretty Print the Commit History
-- Shows each commit on a single line
git log --pretty=oneline

-- Filter Commits by Author
git log --author="Author Name"

-- Filter Commits by Date Range
git log --since="2023-01-01" --until="2023-12-31"

-- Show Changes Introduced by Each Commit
-- Displays the diffs introduced by each commit
git log -p

Example Output

When running git log

git show

Description

It is used to display detailed information about Git objects such as commits, tags, and blobs. It provides a combination of the functionalities of git log and git diff, showing the commit details along with the diff introduced by that commit. It is particularly useful for viewing the content changes and metadata of a specific commit or object.

Usage

git show [<options>] <object>

Options

--pretty=<format>: Specifies the format for displaying commit information. Possible values include oneline, short, medium, full, fuller, email, and raw.

-q or --quiet: Suppresses diff output.

--name-only: Shows only the names of changed files.

--name-status: Shows the names and status of changed files.

--stat: Shows the stats of changes (number of insertions and deletions) introduced by the commit.

git show --pretty=short <commit-hash>
git show -q <commit-hash>
git show --name-only <commit-hash>
git show --name-status <commit-hash>
git show --stat <commit-hash>

What It Does

1. Displays Commit Information: Shows details of the specified commit, including author, date, and commit message.

2. Shows Changes Introduced: Displays the diff of changes introduced by the specified commit.

Commit Hash: The commit hash is a unique identifier for each commit. You can get the commit hash from git log or other Git commands.

Filtering Changes: You can use git show in combination with other options to filter and format the output to meet your specific needs.

Quiet Mode: Using the -q option suppresses the diff output, which can be useful if you're only interested in the commit metadata.

File Path: Specifying a file path limits the output to changes made to that file, helping to narrow down the details if a commit affects multiple files.

Common Use Cases

-- Show a Specific Commit
-- Displays details and changes for the specified commit
git show <commit-hash>

-- Show the Latest Commit
-- Displays details and changes for the most recent commit on the current branch
git show

-- Show a Specific File Change in a Commit
-- Displays the changes for a specific file in the specified commit
git show <commit-hash> -- <file-path>

Example Workflow

-- View the Latest Commit
git show

-- View a Specific Commit
git show 1a2b3c4d

-- View Only the Changed File Names in a Commit
-- This shows the names of the files changed in the specified commit
git show --name-only 1a2b3c4d

-- View a Specific File's Changes in a Commit
-- This shows the changes introduced to path/to/file.txt in the specified commit
git show 1a2b3c4d -- path/to/file.txt

-- View Commit Changes with Statistics
-- This shows the number of insertions and deletions for each file changed in the specified commit
git show --stat 1a2b3c4d

Example Output

When running git show <commit-hash>

git blame

Description

It is used to display the last modification of each line in a file along with the commit, author, and date that introduced the change. This command is particularly useful for identifying who last changed a specific line of code, and when it was changed, which can be valuable for debugging and code review purposes.

Usage

git blame [<options>] <file>

Options

-L <start>,<end>: Limits the blame output to the specified range of lines

-w or --ignore-whitespace: Ignores changes in whitespace

-C: Detects lines that have been moved or copied within the same file

-M: Detects lines that have been moved or copied from other files

--since=<date>: Limits the blame output to changes made since the specified date

--until=<date>: Limits the blame output to changes made until the specified date

--show-name: Shows the file name in the blame output

git blame -L 10,20 path/to/file
git blame -w path/to/file
git blame -C path/to/file
git blame -M path/to/file
git blame --since=2023-01-01 path/to/file
git blame --until=2023-12-31 path/to/file
git blame --show-name path/to/file

What It Does

1. Annotates Each Line: Displays each line of the file with information about the commit, author, and date of the last modification.

2. Helps Track Changes: Identifies who made changes to specific lines and provides context for when and why the changes were made.

Common Use Cases

-- Blame a File
-- Shows the blame information for each line in the specified file
git blame path/to/file

-- Blame a Specific Range of Lines
-- Limits the blame output to a specific range of lines.
git blame -L <start>,<end> path/to/file

-- Ignore Whitespace Changes
-- Ignores changes in whitespace when assigning blame.
git blame -w path/to/file

Example Workflow

-- Blame a File
-- This shows the blame information for each line in README.md
git blame README.md

-- Blame a Specific Range of Lines
-- This limits the blame output to lines 50 through 100 in README.md
git blame -L 50,100 README.md

-- Ignore Whitespace Changes
-- This ignores changes in whitespace when determining blame for README.md
git blame -w README.md

Example Output

When running git blame path/to/file