【问题标题】:How does "index f2e4113..d4b9bfc 100644" in git diff correspond to SHA1 ID in gitk?git diff 中的“index f2e4113..d4b9bfc 100644”如何对应 gitk 中的 SHA1 ID?
【发布时间】:2013-10-07 12:06:06
【问题描述】:

git diff 的输出中的“index f2e4113..d4b9bfc 100644”是什么意思?到目前为止,我一直假设这些 SHA1 ID 是 from_version..to_version,但我在 gitk 中找不到它们。

$ git --version
git version 1.8.3.4
$ git diff ae1fdc1
diff --git a/README b/README
index f2e4113..d4b9bfc 100644
--- a/README
+++ b/README
@@ -1 +1,3 @@
stuff
+more
+more stuff

'index f2e4113..d4b9bfc 100644' 看起来不像 diff 统一格式的一部分。 http://en.wikipedia.org/wiki/Diff#Unified_format

100644 看起来像文件模式,但与 README 文件 (660) 的模式不对应。

f2e4113..d4b9bfc 是 SHA1 ID 短片。 'git rev-parse' 给出了长 SHA1。以下是上述示例中的所有三个矮个子:

ae1fdc1 - ae1fdc1e7b2f018a15c421f2f22b7c77215c5d61
d4b9bfc - d4b9bfcd51a3eaf427d337a30b12d1f3dbdd21b4
f2e4113 - f2e41136eac73c39554dede1fd7e67b12502d577

但为什么 ae1fdc1 不对应差异的第一或第二部分? 为什么我使用 gitk 找不到 d4b9bfc 或 d4b9bfc?

【问题讨论】:

    标签: git gitk


    【解决方案1】:

    编辑:@wiswit 指出了this 很好的解释。

    f2e4113d4b9bfc 是文件索引。使用git show f2e4113,您可以看到提交前的文件,git show d4b9bfc 显示提交后的文件。

    组合 diff 格式在 git diff 手册页中描述。

    COMBINED DIFF FORMAT
       Any diff-generating command can take the ‘-c` or --cc option to produce a 
       combined diff when showing a merge. This is the default format when showing 
       merges with git-diff(1) or git-show(1). Note also that you can give the `-m’
       option to any of these commands to force generation of diffs with individual 
       parents of a merge.
    
       A combined diff format looks like this:
    
           diff --combined describe.c
           index fabadb8,cc95eb0..4866510
           --- a/describe.c
           +++ b/describe.c
           @@@ -98,20 -98,12 +98,20 @@@
                   return (a_date > b_date) ? -1 : (a_date == b_date) ? 0 : 1;
             }
    
           - static void describe(char *arg)
            -static void describe(struct commit *cmit, int last_one)
           ++static void describe(char *arg, int last_one)
             {
            +      unsigned char sha1[20];
            +      struct commit *cmit;
                   struct commit_list *list;
                   static int initialized = 0;
                   struct commit_name *n;
    
            +      if (get_sha1(arg, sha1) < 0)
            +              usage(describe_usage);
            +      cmit = lookup_commit_reference(sha1);
            +      if (!cmit)
            +              usage(describe_usage);
            +
                   if (!initialized) {
                           initialized = 1;
                           for_each_ref(get_name);
    
        1. It is preceded with a "git diff" header, that looks like this (when -c 
           option is used):
    
               diff --combined file
    
           or like this (when --cc option is used):
    
               diff --cc file
    
        2. It is followed by one or more extended header lines (this example shows
           a merge with two parents):
    
               index <hash>,<hash>..<hash>
               mode <mode>,<mode>..<mode>
               new file mode <mode>
               deleted file mode <mode>,<mode>
    
           The mode <mode>,<mode>..<mode> line appears only if at least one of the 
           <mode> is different from the rest. Extended headers with information 
           about  detected contents movement (renames and copying detection) are
           designed to work with diff of two <tree-ish> and are not used by combined
           diff format.
    
        3. It is followed by two-line from-file/to-file header
    
               --- a/file
               +++ b/file
    
           Similar to two-line header for traditional unified diff format, 
           /dev/null is used to signal created or deleted files.
    
        4. Chunk header format is modified to prevent people from accidentally
           feeding it to patch -p1. Combined diff format was created for review 
           of merge commit changes, and was not meant for apply. The change is 
           similar to the change in the extended index header:
    
               @@@ <from-file-range> <from-file-range> <to-file-range> @@@
    
           There are (number of parents + 1) @ characters in the chunk header for 
           combined diff format.
    
       Unlike the traditional unified diff format, which shows two files A and B
       with a single column that has - (minus — appears in A but removed in B),
       + (plus — missing in A but added to B), or " " (space — unchanged) prefix,
       this format compares two or more files file1, file2,... with one file X, 
       and shows how X differs from each of fileN. One column for each of fileN is
       prepended to the output line to note how X’s line is different from it.
    
       A - character in the column N means that the line appears in fileN but it
       does not appear in the result. A + character in the column N means that
       the line appears in the result, and fileN does not have that line (in 
       other words, the line was added, from the point of view of that parent).
    
       In the above example output, the function signature was changed from both
       files (hence two - removals from both file1 and file2, plus ++ to mean one 
       line that was added does not appear in either file1 nor file2). Also eight 
       other lines are the same from file1 but do not appear in file2 (hence 
       prefixed with +).
    
       When shown by git diff-tree -c, it compares the parents of a merge commit
       with the merge result (i.e. file1..fileN are the parents). When shown by 
       git diff-files -c, it compares the two unresolved merge parents with the 
       working tree file (i.e. file1 is stage 2 aka "our version", file2 is stage 
       3 aka "their version").
    

    【讨论】:

    • 现在,在了解它是一个文件索引之后,我在gitk中也看到了这个索引。也可以使用较低的搜索字段来搜索它。 (不是 SHA1 ID 字段。)谢谢。
    • 原始问题中的差异不是组合差异,只是常规的 git 风格差异。 mode100644 而不是 660100660 的原因是 git 仅存储文件 rwx 模式的一位,特别是 x 位。工作副本的模式基于存储的位加上用户的umask 设置。 diff 字符串始终只是 100644100755(对于常规文件)。
    • 您好,这里还有一个简单易懂的介绍:git-tower.com/learn/git/ebook/command-line/advanced-topics/…
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