Git系列讲解 —— 提交日志(git log)的使用

git log命令提供了很多子选项，善于使用这些选项可以加快工程师调查问题的效率，下面以ccache的项目举例讲解。

1. git log

完整的commit id，作者，提交日期，注释

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2. pretty模式 [ git log --pretty= ]

这个pretty可以理解为对git log默认输出的美化，包含几个子选项，使用者可依据自己的需求选择其一使用。

2.1 git log --pretty=email

2.2 git log --pretty=full

2.3 git log --pretty=fuller

2.4 git log --pretty=medium

2.5 git log --pretty=oneline

2.6 git log --pretty=raw

2.7 git log --pretty=short

2.8 git log --pretty=format:

format的选项太多了，这里就不细讲了，下面是从手册中摘抄的说明，读者有时间可以根据自己的需要进行学习。

·   %H: commit hash
·   %h: abbreviated commit hash
·   %T: tree hash
·   %t: abbreviated tree hash
·   %P: parent hashes
·   %p: abbreviated parent hashes
·   %an: author name
·   %aN: author name (respecting .mailmap, see git-shortlog(1) or git-blame(1))
·   %ae: author email
·   %aE: author email (respecting .mailmap, see git-shortlog(1) or git-blame(1))
·   %ad: author date (format respects --date= option)
·   %aD: author date, RFC2822 style
·   %ar: author date, relative
·   %at: author date, UNIX timestamp
·   %ai: author date, ISO 8601-like format
·   %aI: author date, strict ISO 8601 format
·   %cn: committer name
·   %cN: committer name (respecting .mailmap, see git-shortlog(1) or git-blame(1))
·   %ce: committer email
·   %cE: committer email (respecting .mailmap, see git-shortlog(1) or git-blame(1))
·   %cd: committer date (format respects --date= option)
·   %cD: committer date, RFC2822 style
·   %cr: committer date, relative
·   %ct: committer date, UNIX timestamp
·   %ci: committer date, ISO 8601-like format
·   %cI: committer date, strict ISO 8601 format
·   %d: ref names, like the --decorate option of git-log(1)
·   %D: ref names without the " (", ")" wrapping.
·   %e: encoding
·   %s: subject
·   %f: sanitized subject line, suitable for a filename
·   %b: body
·   %B: raw body (unwrapped subject and body)
·   %N: commit notes
·   %GG: raw verification message from GPG for a signed commit
·   %G?: show "G" for a good (valid) signature, "B" for a bad signature, "U" for a good signature with unknown validity, "X" for a good signature that has expired, "Y" for a good
    signature made by an expired key, "R" for a good signature made by a revoked key, "E" if the signature cannot be checked (e.g. missing key) and "N" for no signature
·   %GS: show the name of the signer for a signed commit
·   %GK: show the key used to sign a signed commit
·   %gD: reflog selector, e.g., refs/stash@{1} or refs/stash@{2 minutes ago}; the format follows the rules described for the -g option. The portion before the @ is the refname as given on
    the command line (so git log -g refs/heads/master would yield refs/heads/master@{0}).
·   %gd: shortened reflog selector; same as %gD, but the refname portion is shortened for human readability (so refs/heads/master becomes just master).
·   %gn: reflog identity name
·   %gN: reflog identity name (respecting .mailmap, see git-shortlog(1) or git-blame(1))
·   %ge: reflog identity email
·   %gE: reflog identity email (respecting .mailmap, see git-shortlog(1) or git-blame(1))
·   %gs: reflog subject
·   %Cred: switch color to red
·   %Cgreen: switch color to green
·   %Cblue: switch color to blue
·   %Creset: reset color
·   %C(...): color specification, as described under Values in the "CONFIGURATION FILE" section of git-config(1). By default, colors are shown only when enabled for log output (by
    color.diff, color.ui, or --color, and respecting the auto settings of the former if we are going to a terminal).  %C(auto,...)  is accepted as a historical synonym for the default
    (e.g., %C(auto,red)). Specifying %C(always,...) will show the colors even when color is not otherwise enabled (though consider just using `--color=always to enable color for the whole
    output, including this format and anything else git might color).  auto alone (i.e.  %C(auto)) will turn on auto coloring on the next placeholders until the color is switched again.
·   %m: left (<), right (>) or boundary (-) mark
·   %n: newline
·   %%: a raw %
·   %x00: print a byte from a hex code
·   %w([<w>[,<i1>[,<i2>]]]): switch line wrapping, like the -w option of git-shortlog(1).
·   %<(<N>[,trunc|ltrunc|mtrunc]): make the next placeholder take at least N columns, padding spaces on the right if necessary. Optionally truncate at the beginning (ltrunc), the middle
    (mtrunc) or the end (trunc) if the output is longer than N columns. Note that truncating only works correctly with N >= 2.
·   %<|(<N>): make the next placeholder take at least until Nth columns, padding spaces on the right if necessary
·   %>(<N>), %>|(<N>): similar to %<(<N>), %<|(<N>) respectively, but padding spaces on the left
·   %>>(<N>), %>>|(<N>): similar to %>(<N>), %>|(<N>) respectively, except that if the next placeholder takes more spaces than given and there are spaces on its left, use those spaces
·   %><(<N>), %><|(<N>): similar to %<(<N>), %<|(<N>) respectively, but padding both sides (i.e. the text is centered)
·   %(trailers[:options]): display the trailers of the body as interpreted by git-interpret-trailers(1). The trailers string may be followed by a colon and zero or more comma-separated
    options. If the only option is given, omit non-trailer lines from the trailer block. If the unfold option is given, behave as if interpret-trailer’s --unfold option was given. E.g.,
    %(trailers:only,unfold) to do both.
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3. 单行输出

3.1 git log --oneline

和git log --pretty=oneline差不多，都是每笔提交一行输出(commitID comment)，不同的是git log --oneline的commit id是缩写的。

当第一行注释和第二行注释之间有空行，就只会显示第一行注释，比如下图的最新提交(80a228c3)，对照git log默认输出的就只显示了第一行注释。

3.2 git log --oneline

以单行模式输出某文件的所有提交记录。

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4. 输出每笔提交内容变更量统计

4.1 git log --stat

4.2 git log --stat

输出某文件的所有提交记录及其变更量统计。

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5. 输出所有提交的变更内容

5.1 git log -p

输出每笔提交的记录以及其变更内容

5.2 git log -p

输出某文件的所有提交记录及其变更内容。

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6. 显示某笔提交的变更情况 [ git show --stat commitID ]

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7. 显示某笔提交的变更内容 [ git show commitID ]

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8. 指定日期格式 [ git log --date= ]

命令后接下面选项：

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9. 依据某条件筛选显示

案例：
现有一个git仓库，master分支包含了笔提交，管理两个文件（1.txt，2.txt）。

git log --grep="modify 1.txt"

查找commit message中包含"modify 1.txt"的提交。

git log -S "testvar = 1"

我们知道每笔提交都包含文件内容的变更(增加和删除)，-S的作用就是从这些变更内容中找到要查找的内容(testvar = 1)，并将其git日志输出来。注意要和--grep区分开来，--grep搜索的是提交信息，而-S是搜索提交中的变更内容（git管理的文件，代码等）

我们把上面命令稍作修改，变成 git log -S "testvar = 1" --pretty="%H" | xargs git show，这样就可以看到-S筛选出来的三笔提交，其变更内容都是包含了指定内容（testvar = 1）

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10. 输出文件每行的提交记录

10.1 git blame

输出指定文件中每行内容的最近一笔提交信息。

10.2 git blame -L <开始行数>,<结束行数>

输出某文件从第几行到第几行的最近一笔提交记录

git blame -L 5,5               代表第5行的提交记录
git blame  | tail -n <行数>     搭配tail命令还可以显示最后多少行的提交记录
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