composer source 和 dist。

下载包的方式有两种： source 和 dist。

对于稳定版本 composer 将默认使用 dist 方式，而 source 表示版本控制源 。
–prefer-source：composer 将从 source 安装（如果有的话）。如果想要使用一个 bugfix 到你的项目，这是非常有用的。并且可以直接从本地的版本库直接获取依赖关系。

–prefer-dist：与 –prefer-source 相反，composer 将尽可能的从 dist 获取，这将大幅度的加快在 build servers 上的安装。这也是一个回避 git 问题的途径，如果你不清楚如何正确的设置。

source 可以理解成直接从git服务器(比如：github)获取源代码，这样如果git有提交，那么可以迅速获得最新代码，但是下载速度会慢，国内你懂的。

dist 可以理解成composer有编译服务器，如果从编译服务器获取，那么就可以绕开git服务器了，这样下载速度会更快，但是提交的代码会有延迟。

https://docs.phpcomposer.com/03-cli.html

–prefer-dist 会从github 上下载.zip压缩包，并缓存到本地。下次再安装就会从本地加载，大大加速安装速度。但她没有保留 .git文件夹,没有版本信息。适合基于这个package进行开发。

–prefer-source 会从github 上clone 源代码，不会在本地缓存。但她保留了.git文件夹，从而可以实现版本控制。适合用于修改源代码。

接下来我们进行验证。

1 准备测试环境和数据
1.1 新建一个测试项目，并指定依赖包 twig
[ahcj@localhost test]$ mkdir composer-test
[ahcj@localhost test]$ cd composer-test/
[ahcj@localhost composer-test]$ composer init –require=”twig/twig:1.*” -n –profile
[6.1MB/0.00s] Memory usage: 6.07MB (peak: 6.17MB), time: 0s

1.2 确定缓存目录 cache-files-dir 为 /home/ahcj/.cache/composer/files
[ahcj@localhost ~]$ /usr/bin/composer config –list
[repositories.packagist.org.type] composer
[repositories.packagist.org.url] https?://packagist.org
[repositories.packagist.org.allow_ssl_downgrade] true
[process-timeout] 300
[use-include-path] false
[preferred-install] auto
[notify-on-install] true
[github-protocols] [https, ssh]
[vendor-dir] vendor (/home/ahcj/vendor)
[bin-dir] {$vendor-dir}/bin (/home/ahcj/vendor/bin)
[cache-dir] /home/ahcj/.cache/composer
[data-dir] /home/ahcj/.local/share/composer
[cache-files-dir] {$cache-dir}/files (/home/ahcj/.cache/composer/files)
….省略….

1.3 查找是否有twig的缓存
[ahcj@localhost coposertest]$ ll /home/ahcj/.cache/composer/files/twig
ls: 无法访问/home/ahcj/.cache/composer/files/twig: 没有那个文件或目录
2 测试 –prefer-source
2.1 使用 –prefer-source 安装,用了 31.26s
[ahcj@localhost composer-test]$ composer install –profile –prefer-source
[6.1MB/0.00s] Loading composer repositories with package information
[6.4MB/6.08s] Updating dependencies (including require-dev)
[102.7MB/18.84s] Package operations: 1 install, 0 updates, 0 removals
[102.7MB/18.84s] - Installing twig/twig (v1.34.4): [102.8MB/20.76s] Cloning f878bab48e from cache
[101.3MB/31.26s] Writing lock file
[101.3MB/31.26s] Generating autoload files
[101.3MB/31.26s] Memory usage: 101.31MB (peak: 109.88MB), time: 31.26s
2.2 删除 vendor 目录，重新使用 –prefer-source 安装,用了 33.64s，基本没有差别
[ahcj@localhost composer-test]$ rm -rf vendor
[ahcj@localhost composer-test]$ composer install –profile –prefer-source
[6.2MB/0.01s] Loading composer repositories with package information
[6.3MB/0.01s] Installing dependencies (including require-dev) from lock file
[6.8MB/0.02s] Package operations: 1 install, 0 updates, 0 removals
[6.8MB/0.02s] - Installing twig/twig (v1.34.4): [6.9MB/12.90s] Cloning f878bab48e from cache
[6.8MB/33.64s] Generating autoload files
[6.8MB/33.64s] Memory usage: 6.82MB (peak: 6.98MB), time: 33.64s
2.3 查看发现没有缓存，都是直接下载的麻。
[ahcj@localhost composer-test]$ ll /home/ahcj/.cache/composer/files/twig
ls: 无法访问/home/ahcj/.cache/composer/files/twig: 没有那个文件或目录
2.4 发现了版本控制信息
[ahcj@localhost composer-test]$ find -name .git
./vendor/twig/twig/.git
[ahcj@localhost composer-test]$ cd ./vendor/twig/twig/
[ahcj@localhost twig]$ git log | less
….好多，通通省略….
3 使用 –prefer-dist 安装
3.1 使用 –prefer-dist 安装,用了 20.34s
[ahcj@localhost composer-test]$ rm -rf vendor
[ahcj@localhost composer-test]$ composer install –profile –prefer-dist
[6.2MB/0.00s] Loading composer repositories with package information
[6.3MB/0.01s] Installing dependencies (including require-dev) from lock file
[6.8MB/0.01s] Package operations: 1 install, 0 updates, 0 removals
[6.8MB/0.01s] - Installing twig/twig (v1.34.4): [7.0MB/0.01s] D[7.0MB/12.99s] Downloading (0%)[7.0MB/12.99s] [7.0MB/14.48s] Downloading (5%[7.0MB/15.35s] Downloading (10[7.1MB/16.00s] Downloading (15[7.1MB/16.44s] Downloading (20%)[7.[7.1MB/16.86s] Downloading (25[7.1MB/17.08s] Downloading (30[7.2MB/17.50s] Downloading (35[7.2MB/17.71s] Downloading (40%)[7.[7.2MB/17.73s] Downloading (45[7.3MB/17.95s] Downloading (50[7.3MB/18.14s] Downloading (55[7.3MB/18.17s] Downloading (60%)[7.[7.3MB/18.36s] Downloading (65[7.4MB/18.38s] Downloading (70[7.4MB/18.57s] Downloading (75[7.4MB/18.59s] Downloading (80%)[7.[7.5MB/18.61s] Downloading (85[7.5MB/18.80s] Downloading (90[7.5MB/18.82s] Downloading (95[7.5MB/18.86s] Downloading (100%)[7.0MB/18.86s]
[6.8MB/20.34s] Generating autoload files
[6.8MB/20.34s] Memory usage: 6.84MB (peak: 8.12MB), time: 20.34s

3.2 找到了缓存
[ahcj@localhost composer-test]$ ll /home/ahcj/.cache/composer/files/twig
ls: 无法访问/home/ahcj/.cache/composer/files/twig: 没有那个文件或目录
[ahcj@localhost composer-test]$ ll /home/ahcj/.cache/composer/files/twig
总用量 0
drwxrwxr-x 2 ahcj ahcj 58 8月 18 12:16 twig

3.3 重新使用 –prefer-dist 安装，这次用了 6.43s，只有上次安装的 1/4 时间
[ahcj@localhost composer-test]$ rm -rf vendor
[ahcj@localhost composer-test]$ composer install –profile –prefer-dist
[6.3MB/0.01s] Loading composer repositories with package information
[6.4MB/0.01s] Installing dependencies (including require-dev) from lock file
[6.9MB/0.01s] Package operations: 1 install, 0 updates, 0 removals
[6.9MB/0.02s] - Installing twig/twig (v1.34.4): [7.0MB/0.02s] Loading from cache[7.0MB/0.02s]
[6.9MB/6.43s] Generating autoload files
[6.9MB/6.43s] Memory usage: 6.87MB (peak: 7.13MB), time: 6.43s
3.4 并没有 .git 版本控制信息哟
[ahcj@localhost composer-test]$ find -name .git

https://docs.phpcomposer.com/articles/aliases.html

如果要对一个资源包使用行内别名，这个别名（as 的右边）必须能够使用版本约束。as 左边的部分在这之后将被丢弃。因此，如果 A 依赖 B 而 B 又依赖 monolog/monolog 且版本约束为 dev-bugfix as 1.0.x-dev，那么安装 A 时将使用 B 的版本约束，并识别为 1.0.x-dev，此时必须真实存在一个“分支别名”或“1.0 系列分支”。否则就必须在 A 的 composer.json 文件中再次定义行内别名。

“dev-master”永远大于所有版本号

嵌套依赖情况可以vcs方式，且 被依赖的包在require 里加上 dev－master