log command

The log command is used to view the commit history of a repository. It displays:

The commit hash (SHA-1 identifier)
The author of the commit
The commit timestamp
The commit message

Command Implementation

Check if .mygit/HEAD exists:

./index.php
if (!file_exists(".mygit/HEAD")) {
  echo "Error: No commits yet\n";
  return;
}

Ensures that the repository has at least one commit.
If .mygit/HEAD doesn’t exist, no commits have been made, so it prints an error and exits.

Determine the latest commit hash:

./index.php
$head_content = trim(file_get_contents(".mygit/HEAD"));
$curr_hash = null;

if (str_starts_with($head_content, "ref: ")) {
  $ref = substr($head_content, 5);
  if (!file_exists(".mygit/" . $ref)) {
    echo "Error: No commits yet\n";
    return;
  }
  $curr_hash = trim(file_get_contents(".mygit/" . $ref));
} else {
  $curr_hash = $head_content;
}

Reads .mygit/HEAD, which stores either:
- A reference (ref: refs/heads/main), pointing to a branch’s latest commit.
- A direct commit hash (in a detached HEAD state).
If it’s a reference, we retrieve the latest commit hash from .mygit/refs/heads/main.
Otherwise, we assume that .mygit/HEAD contains a commit hash.

Iterate through the commit history:

./index.php
while ($curr_hash) {

The loop iterates over commit objects, starting from $curr_hash (latest commit) and following parent commits.

Retrieve and uncompress the commit object:

./index.php
$dir = ".mygit/objects/" . substr($curr_hash, 0, 2);
$path = $dir . '/' . substr($curr_hash, 2);

if (!file_exists($path)) {
  echo "Error: Commit object not found\n";
  break;
}

$compressed = file_get_contents($path);
$data = gzuncompress($compressed);
$parts = explode("\0", $data, 2);

if (count($parts) < 2) {
  echo "Error: Invalid commit object format\n";
  break;
}

we construct the path to the commit object by using the first two characters of the hash as the directory name and the rest as file path.
Reads and uncompresses the commit object.
Splits the content at the \0 null byte (used to separate the header and commit content).
If the commit object format is invalid, it prints an error and exits.

Extract commit metadata:
1. Extract the content:
./index.php
```
$content = $parts[1];
$lines = explode("\n", $content);
```
- $parts[1] contains everything after the \0, which the actual commit metadata and message.
- Then we split the content into lines.
1. Initialize variables:
./index.php
```
$commit_data = [];
$message = "";
$reading_message = false;
```
- $commit_data will store key-value pairs of commit metadata (tree, parent, author).
- $message will store the commit message.
- $reading_message is a flag to track when we start reading the message.
1. Process each line:
./index.php
```
foreach ($lines as $line) {
  if (empty(trim($line))) continue;
```
- We skip empty lines to avoid unnecessary processing.
1. Handle the commit message:
./index.php
```
if (str_starts_with($line, "message ")) {
  $message = substr($line, 8);
  $reading_message = true;
} else if ($reading_message) {
  $message .= "\n" . $line;
} else {
  $parts = explode(" ", $line, 2);
  if (count($parts) == 2) {
    $commit_data[$parts[0]] = $parts[1];
  }
}
```
- If the line starts with "message ", it marks the beginning of the commit message.
- We use substr($line, 8) to remove "message " and stores the actual message.
- If $reading_message is already true, additional lines are appended to $message (we use it to handle multi-line commit messages).
- Else if a line isn’t part of the message, we store it as a key-value pair after separating it into parts.
Example of what's stored in our variables after processing:
example
```
$commit_data = [
  "tree" => "a1b2c3d4e5f6g7h8i9j0k1l2m3n4o5p6q7r8s",
  "parent" => "7a1b2c3d4e5f6g7h8i9j0k1l2m3n4o5p6q7r8s",
  "author" => "John Doe john@example.com 1707301245"
];

$message = "Fixed a major bug\nthat caused a crash.";
```

This part code:

./index.php
$content = $parts[1];
$lines = explode("\n", $content);

$commit_data = [];
$message = "";
$reading_message = false;

foreach ($lines as $line) {
  if (empty(trim($line))) continue;

  if (str_starts_with($line, "message ")) {
    $message = substr($line, 8);
    $reading_message = true;
  } else if ($reading_message) {
    $message .= "\n" . $line;
  } else {
    $parts = explode(" ", $line, 2);
    if (count($parts) == 2) {
      $commit_data[$parts[0]] = $parts[1];
    }
  }
}

Print commit data:

./index.php
echo "\033[33mcommit " . $curr_hash . "\033[0m\n";

if (isset($commit_data["author"])) {
  $author_data = explode(" ", $commit_data["author"]);
  $timestamp = end($author_data);
  $author_name = implode(" ", array_slice($author_data, 0, -1));
  $date = date("Y-m-d H:i:s", (int) $timestamp) . "\n";
}
echo "\033[36mAuthor: " . $author_name . "\033[0m\n";
echo "Date: " . $date;
echo "\n      " . $message . "\n\n";

Prints the commit hash in yellow (\033[33m).
We extracts the author's name and timestamp.
Then we convert the timestamp into a human-readable format (YYYY-MM-DD HH:MM:SS).
Prints the author’s name in cyan (\033[36m).
Prints the commit message.

Move to the parent commit:

./index.php
$curr_hash = $commit_data["parent"] ?? null;

Sets $curr_hash to the parent commit hash.
If no parent exists, it stops our while loop.

Full code for this section:

./index.php
function command_log()
{
  if (!file_exists(".mygit/HEAD")) {
    echo "Error: No commits yet\n";
    return;
  }

  $head_content = trim(file_get_contents(".mygit/HEAD"));
  $curr_hash = null;

  if (str_starts_with($head_content, "ref: ")) {
    $ref = substr($head_content, 5);
    if (!file_exists(".mygit/" . $ref)) {
      echo "Error: No commits yet\n";
      return;
    }
    $curr_hash = trim(file_get_contents(".mygit/" . $ref));
  } else {
    $curr_hash = $head_content;
  }

  while ($curr_hash) {
    $dir = ".mygit/objects/" . substr($curr_hash, 0, 2);
    $path = $dir . '/' . substr($curr_hash, 2);

    if (!file_exists($path)) {
      echo "Error: Commit object not found\n";
      break;
    }

    $compressed = file_get_contents($path);
    $data = gzuncompress($compressed);
    $parts = explode("\0", $data, 2);

    if (count($parts) < 2) {
      echo "Error: Invalid commit object format\n";
      break;
    }

    $content = $parts[1];
    $lines = explode("\n", $content);

    $commit_data = [];
    $message = "";
    $reading_message = false;

    foreach ($lines as $line) {
      if (empty(trim($line)))
        continue;

      if (str_starts_with($line, "message ")) {
        $message = substr($line, 8);
        $reading_message = true;
      } else if ($reading_message) {
        $message .= "\n" . $line;
      } else {
        $parts = explode(" ", $line, 2);
        if (count($parts) == 2) {
          $commit_data[$parts[0]] = $parts[1];
        }
      }

    }

    echo "\033[33mcommit " . $curr_hash . "\033[0m\n";

    if (isset($commit_data["author"])) {
      $author_data = explode(" ", $commit_data["author"]);
      $timestamp = end($author_data);
      $author_name = implode(" ", array_slice($author_data, 0, -1));
      $date = date("Y-m-d H:i:s", (int) $timestamp) . "\n";
    }
    echo "\033[36mAuthor: " . $author_name . "\033[0m\n";
    echo "Date: " . $date;
    echo "\n      " . $message . "\n\n";

    $curr_hash = $commit_data["parent"] ?? null;
  }

}

Command Implementation​

Command Implementation