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diff --git a/www/wiki/includes/GitInfo.php b/www/wiki/includes/GitInfo.php
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+<?php
+/**
+ * A class to help return information about a git repo MediaWiki may be inside
+ * This is used by Special:Version and is also useful for the LocalSettings.php
+ * of anyone working on large branches in git to setup config that show up only
+ * when specific branches are currently checked out.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ */
+
+use MediaWiki\Shell\Shell;
+
+class GitInfo {
+
+	/**
+	 * Singleton for the repo at $IP
+	 */
+	protected static $repo = null;
+
+	/**
+	 * Location of the .git directory
+	 */
+	protected $basedir;
+
+	/**
+	 * Location of the repository
+	 */
+	protected $repoDir;
+
+	/**
+	 * Path to JSON cache file for pre-computed git information.
+	 */
+	protected $cacheFile;
+
+	/**
+	 * Cached git information.
+	 */
+	protected $cache = [];
+
+	/**
+	 * @var array|false Map of repo URLs to viewer URLs. Access via static method getViewers().
+	 */
+	private static $viewers = false;
+
+	/**
+	 * @param string $repoDir The root directory of the repo where .git can be found
+	 * @param bool $usePrecomputed Use precomputed information if available
+	 * @see precomputeValues
+	 */
+	public function __construct( $repoDir, $usePrecomputed = true ) {
+		$this->repoDir = $repoDir;
+		$this->cacheFile = self::getCacheFilePath( $repoDir );
+		wfDebugLog( 'gitinfo',
+			"Computed cacheFile={$this->cacheFile} for {$repoDir}"
+		);
+		if ( $usePrecomputed &&
+			$this->cacheFile !== null &&
+			is_readable( $this->cacheFile )
+		) {
+			$this->cache = FormatJson::decode(
+				file_get_contents( $this->cacheFile ),
+				true
+			);
+			wfDebugLog( 'gitinfo', "Loaded git data from cache for {$repoDir}" );
+		}
+
+		if ( !$this->cacheIsComplete() ) {
+			wfDebugLog( 'gitinfo', "Cache incomplete for {$repoDir}" );
+			$this->basedir = $repoDir . DIRECTORY_SEPARATOR . '.git';
+			if ( is_readable( $this->basedir ) && !is_dir( $this->basedir ) ) {
+				$GITfile = file_get_contents( $this->basedir );
+				if ( strlen( $GITfile ) > 8 &&
+					substr( $GITfile, 0, 8 ) === 'gitdir: '
+				) {
+					$path = rtrim( substr( $GITfile, 8 ), "\r\n" );
+					if ( $path[0] === '/' || substr( $path, 1, 1 ) === ':' ) {
+						// Path from GITfile is absolute
+						$this->basedir = $path;
+					} else {
+						$this->basedir = $repoDir . DIRECTORY_SEPARATOR . $path;
+					}
+				}
+			}
+		}
+	}
+
+	/**
+	 * Compute the path to the cache file for a given directory.
+	 *
+	 * @param string $repoDir The root directory of the repo where .git can be found
+	 * @return string Path to GitInfo cache file in $wgGitInfoCacheDirectory or
+	 * fallback in the extension directory itself
+	 * @since 1.24
+	 */
+	protected static function getCacheFilePath( $repoDir ) {
+		global $IP, $wgGitInfoCacheDirectory;
+
+		if ( $wgGitInfoCacheDirectory ) {
+			// Convert both $IP and $repoDir to canonical paths to protect against
+			// $IP having changed between the settings files and runtime.
+			$realIP = realpath( $IP );
+			$repoName = realpath( $repoDir );
+			if ( $repoName === false ) {
+				// Unit tests use fake path names
+				$repoName = $repoDir;
+			}
+			if ( strpos( $repoName, $realIP ) === 0 ) {
+				// Strip $IP from path
+				$repoName = substr( $repoName, strlen( $realIP ) );
+			}
+			// Transform path to git repo to something we can safely embed in
+			// a filename
+			$repoName = strtr( $repoName, DIRECTORY_SEPARATOR, '-' );
+			$fileName = 'info' . $repoName . '.json';
+			$cachePath = "{$wgGitInfoCacheDirectory}/{$fileName}";
+			if ( is_readable( $cachePath ) ) {
+				return $cachePath;
+			}
+		}
+
+		return "$repoDir/gitinfo.json";
+	}
+
+	/**
+	 * Get the singleton for the repo at $IP
+	 *
+	 * @return GitInfo
+	 */
+	public static function repo() {
+		if ( is_null( self::$repo ) ) {
+			global $IP;
+			self::$repo = new self( $IP );
+		}
+		return self::$repo;
+	}
+
+	/**
+	 * Check if a string looks like a hex encoded SHA1 hash
+	 *
+	 * @param string $str The string to check
+	 * @return bool Whether or not the string looks like a SHA1
+	 */
+	public static function isSHA1( $str ) {
+		return !!preg_match( '/^[0-9A-F]{40}$/i', $str );
+	}
+
+	/**
+	 * Get the HEAD of the repo (without any opening "ref: ")
+	 *
+	 * @return string|bool The HEAD (git reference or SHA1) or false
+	 */
+	public function getHead() {
+		if ( !isset( $this->cache['head'] ) ) {
+			$headFile = "{$this->basedir}/HEAD";
+			$head = false;
+
+			if ( is_readable( $headFile ) ) {
+				$head = file_get_contents( $headFile );
+
+				if ( preg_match( "/ref: (.*)/", $head, $m ) ) {
+					$head = rtrim( $m[1] );
+				} else {
+					$head = rtrim( $head );
+				}
+			}
+			$this->cache['head'] = $head;
+		}
+		return $this->cache['head'];
+	}
+
+	/**
+	 * Get the SHA1 for the current HEAD of the repo
+	 *
+	 * @return string|bool A SHA1 or false
+	 */
+	public function getHeadSHA1() {
+		if ( !isset( $this->cache['headSHA1'] ) ) {
+			$head = $this->getHead();
+			$sha1 = false;
+
+			// If detached HEAD may be a SHA1
+			if ( self::isSHA1( $head ) ) {
+				$sha1 = $head;
+			} else {
+				// If not a SHA1 it may be a ref:
+				$refFile = "{$this->basedir}/{$head}";
+				$packedRefs = "{$this->basedir}/packed-refs";
+				$headRegex = preg_quote( $head, '/' );
+				if ( is_readable( $refFile ) ) {
+					$sha1 = rtrim( file_get_contents( $refFile ) );
+				} elseif ( is_readable( $packedRefs ) &&
+					preg_match( "/^([0-9A-Fa-f]{40}) $headRegex$/m", file_get_contents( $packedRefs ), $matches )
+				) {
+					$sha1 = $matches[1];
+				}
+			}
+			$this->cache['headSHA1'] = $sha1;
+		}
+		return $this->cache['headSHA1'];
+	}
+
+	/**
+	 * Get the commit date of HEAD entry of the git code repository
+	 *
+	 * @since 1.22
+	 * @return int|bool Commit date (UNIX timestamp) or false
+	 */
+	public function getHeadCommitDate() {
+		global $wgGitBin;
+
+		if ( !isset( $this->cache['headCommitDate'] ) ) {
+			$date = false;
+			if ( is_file( $wgGitBin ) &&
+				is_executable( $wgGitBin ) &&
+				!Shell::isDisabled() &&
+				$this->getHead() !== false
+			) {
+				$cmd = [
+					$wgGitBin,
+					'show',
+					'-s',
+					'--format=format:%ct',
+					'HEAD',
+				];
+				$gitDir = realpath( $this->basedir );
+				$result = Shell::command( $cmd )
+					->environment( [ 'GIT_DIR' => $gitDir ] )
+					->restrict( Shell::RESTRICT_DEFAULT | Shell::NO_NETWORK )
+					->whitelistPaths( [ $gitDir, $this->repoDir ] )
+					->execute();
+
+				if ( $result->getExitCode() === 0 ) {
+					$date = (int)$result->getStdout();
+				}
+			}
+			$this->cache['headCommitDate'] = $date;
+		}
+		return $this->cache['headCommitDate'];
+	}
+
+	/**
+	 * Get the name of the current branch, or HEAD if not found
+	 *
+	 * @return string|bool The branch name, HEAD, or false
+	 */
+	public function getCurrentBranch() {
+		if ( !isset( $this->cache['branch'] ) ) {
+			$branch = $this->getHead();
+			if ( $branch &&
+				preg_match( "#^refs/heads/(.*)$#", $branch, $m )
+			) {
+				$branch = $m[1];
+			}
+			$this->cache['branch'] = $branch;
+		}
+		return $this->cache['branch'];
+	}
+
+	/**
+	 * Get an URL to a web viewer link to the HEAD revision.
+	 *
+	 * @return string|bool String if a URL is available or false otherwise
+	 */
+	public function getHeadViewUrl() {
+		$url = $this->getRemoteUrl();
+		if ( $url === false ) {
+			return false;
+		}
+		foreach ( self::getViewers() as $repo => $viewer ) {
+			$pattern = '#^' . $repo . '$#';
+			if ( preg_match( $pattern, $url, $matches ) ) {
+				$viewerUrl = preg_replace( $pattern, $viewer, $url );
+				$headSHA1 = $this->getHeadSHA1();
+				$replacements = [
+					'%h' => substr( $headSHA1, 0, 7 ),
+					'%H' => $headSHA1,
+					'%r' => urlencode( $matches[1] ),
+					'%R' => $matches[1],
+				];
+				return strtr( $viewerUrl, $replacements );
+			}
+		}
+		return false;
+	}
+
+	/**
+	 * Get the URL of the remote origin.
+	 * @return string|bool String if a URL is available or false otherwise.
+	 */
+	protected function getRemoteUrl() {
+		if ( !isset( $this->cache['remoteURL'] ) ) {
+			$config = "{$this->basedir}/config";
+			$url = false;
+			if ( is_readable( $config ) ) {
+				Wikimedia\suppressWarnings();
+				$configArray = parse_ini_file( $config, true );
+				Wikimedia\restoreWarnings();
+				$remote = false;
+
+				// Use the "origin" remote repo if available or any other repo if not.
+				if ( isset( $configArray['remote origin'] ) ) {
+					$remote = $configArray['remote origin'];
+				} elseif ( is_array( $configArray ) ) {
+					foreach ( $configArray as $sectionName => $sectionConf ) {
+						if ( substr( $sectionName, 0, 6 ) == 'remote' ) {
+							$remote = $sectionConf;
+						}
+					}
+				}
+
+				if ( $remote !== false && isset( $remote['url'] ) ) {
+					$url = $remote['url'];
+				}
+			}
+			$this->cache['remoteURL'] = $url;
+		}
+		return $this->cache['remoteURL'];
+	}
+
+	/**
+	 * Check to see if the current cache is fully populated.
+	 *
+	 * Note: This method is public only to make unit testing easier. There's
+	 * really no strong reason that anything other than a test should want to
+	 * call this method.
+	 *
+	 * @return bool True if all expected cache keys exist, false otherwise
+	 */
+	public function cacheIsComplete() {
+		return isset( $this->cache['head'] ) &&
+			isset( $this->cache['headSHA1'] ) &&
+			isset( $this->cache['headCommitDate'] ) &&
+			isset( $this->cache['branch'] ) &&
+			isset( $this->cache['remoteURL'] );
+	}
+
+	/**
+	 * Precompute and cache git information.
+	 *
+	 * Creates a JSON file in the cache directory associated with this
+	 * GitInfo instance. This cache file will be used by subsequent GitInfo objects referencing
+	 * the same directory to avoid needing to examine the .git directory again.
+	 *
+	 * @since 1.24
+	 */
+	public function precomputeValues() {
+		if ( $this->cacheFile !== null ) {
+			// Try to completely populate the cache
+			$this->getHead();
+			$this->getHeadSHA1();
+			$this->getHeadCommitDate();
+			$this->getCurrentBranch();
+			$this->getRemoteUrl();
+
+			if ( !$this->cacheIsComplete() ) {
+				wfDebugLog( 'gitinfo',
+					"Failed to compute GitInfo for \"{$this->basedir}\""
+				);
+				return;
+			}
+
+			$cacheDir = dirname( $this->cacheFile );
+			if ( !file_exists( $cacheDir ) &&
+				!wfMkdirParents( $cacheDir, null, __METHOD__ )
+			) {
+				throw new MWException( "Unable to create GitInfo cache \"{$cacheDir}\"" );
+			}
+
+			file_put_contents( $this->cacheFile, FormatJson::encode( $this->cache ) );
+		}
+	}
+
+	/**
+	 * @see self::getHeadSHA1
+	 * @return string
+	 */
+	public static function headSHA1() {
+		return self::repo()->getHeadSHA1();
+	}
+
+	/**
+	 * @see self::getCurrentBranch
+	 * @return string
+	 */
+	public static function currentBranch() {
+		return self::repo()->getCurrentBranch();
+	}
+
+	/**
+	 * @see self::getHeadViewUrl()
+	 * @return bool|string
+	 */
+	public static function headViewUrl() {
+		return self::repo()->getHeadViewUrl();
+	}
+
+	/**
+	 * Gets the list of repository viewers
+	 * @return array
+	 */
+	protected static function getViewers() {
+		global $wgGitRepositoryViewers;
+
+		if ( self::$viewers === false ) {
+			self::$viewers = $wgGitRepositoryViewers;
+			Hooks::run( 'GitViewers', [ &self::$viewers ] );
+		}
+
+		return self::$viewers;
+	}
+}