| Generating patches with -p |
| -------------------------- |
| |
| When "git-diff-index", "git-diff-tree", or "git-diff-files" are run |
| with a `-p` option, "git diff" without the `--raw` option, or |
| "git log" with the "-p" option, they |
| do not produce the output described above; instead they produce a |
| patch file. You can customize the creation of such patches via the |
| `GIT_EXTERNAL_DIFF` and the `GIT_DIFF_OPTS` environment variables. |
| |
| What the -p option produces is slightly different from the traditional |
| diff format: |
| |
| 1. It is preceded with a "git diff" header that looks like this: |
| |
| diff --git a/file1 b/file2 |
| + |
| The `a/` and `b/` filenames are the same unless rename/copy is |
| involved. Especially, even for a creation or a deletion, |
| `/dev/null` is _not_ used in place of the `a/` or `b/` filenames. |
| + |
| When rename/copy is involved, `file1` and `file2` show the |
| name of the source file of the rename/copy and the name of |
| the file that rename/copy produces, respectively. |
| |
| 2. It is followed by one or more extended header lines: |
| |
| old mode <mode> |
| new mode <mode> |
| deleted file mode <mode> |
| new file mode <mode> |
| copy from <path> |
| copy to <path> |
| rename from <path> |
| rename to <path> |
| similarity index <number> |
| dissimilarity index <number> |
| index <hash>..<hash> <mode> |
| + |
| File modes are printed as 6-digit octal numbers including the file type |
| and file permission bits. |
| + |
| Path names in extended headers do not include the `a/` and `b/` prefixes. |
| + |
| The similarity index is the percentage of unchanged lines, and |
| the dissimilarity index is the percentage of changed lines. It |
| is a rounded down integer, followed by a percent sign. The |
| similarity index value of 100% is thus reserved for two equal |
| files, while 100% dissimilarity means that no line from the old |
| file made it into the new one. |
| + |
| The index line includes the SHA-1 checksum before and after the change. |
| The <mode> is included if the file mode does not change; otherwise, |
| separate lines indicate the old and the new mode. |
| |
| 3. TAB, LF, double quote and backslash characters in pathnames |
| are represented as `\t`, `\n`, `\"` and `\\`, respectively. |
| If there is need for such substitution then the whole |
| pathname is put in double quotes. |
| |
| 4. All the `file1` files in the output refer to files before the |
| commit, and all the `file2` files refer to files after the commit. |
| It is incorrect to apply each change to each file sequentially. For |
| example, this patch will swap a and b: |
| |
| diff --git a/a b/b |
| rename from a |
| rename to b |
| diff --git a/b b/a |
| rename from b |
| rename to a |
| |
| |
| 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 linkgit:git-diff[1] or |
| linkgit: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 or 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"). |