The documentation of -S and -G is very sketchy. Completely rewrite the sections in Documentation/diff-options.txt and Documentation/gitdiffcore.txt.
References: 52e9578 ([PATCH] Introducing software archaeologist's tool "pickaxe".) f506b8e (git log/diff: add -G<regexp> that greps in the patch text) Inputs-from: Phil Hord <phil.h...@gmail.com> Co-authored-by: Junio C Hamano <gits...@pobox.com> Signed-off-by: Ramkumar Ramachandra <artag...@gmail.com> --- Documentation/diff-options.txt | 38 +++++++++++++++++++++++++++++-------- Documentation/gitdiffcore.txt | 43 ++++++++++++++++++++++++------------------ 2 files changed, 55 insertions(+), 26 deletions(-) diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt index 104579d..2835eef 100644 --- a/Documentation/diff-options.txt +++ b/Documentation/diff-options.txt @@ -383,14 +383,36 @@ ifndef::git-format-patch that matches other criteria, nothing is selected. -S<string>:: - Look for differences that introduce or remove an instance of - <string>. Note that this is different than the string simply - appearing in diff output; see the 'pickaxe' entry in - linkgit:gitdiffcore for more details. + Look for differences that change the number of occurrences of + the specified string (i.e. addition/deletion) in a file. + Intended for the scripter's use. ++ +It is especially useful when you're looking for an exact block of code +(like a struct), and want to know the history of that block since it +first came into being: use the feature iteratively to feed the +interesting block in the preimage back into `-S`, and keep going until +you get the very first version of the block. -G<regex>:: - Look for differences whose added or removed line matches - the given <regex>. + Look for differences whose patch text contains added/removed + lines that match <regex>. ++ +To illustrate the difference between `-S<regex> --pickaxe-regex` and +`-G<regex>`, consider a commit with the following diff in the same +file: ++ +---- ++ return !regexec(regexp, two->ptr, 1, ®match, 0); +... +- hit = !regexec(regexp, mf2.ptr, 1, ®match, 0); +---- ++ +While `git log -G"regexec\(regexp"` will show this commit, `git log +-S"regexec\(regexp" --pickaxe-regex` will not (because the number of +occurrences of that string did not change). ++ +See the 'pickaxe' entry in linkgit:gitdiffcore for more +information. --pickaxe-all:: When `-S` or `-G` finds a change, show all the changes in that @@ -398,8 +420,8 @@ ifndef::git-format-patch in <string>. --pickaxe-regex:: - Make the <string> not a plain string but an extended POSIX - regex to match. + Treat the <string> given to `-S` as an extended POSIX regular + expression to match. endif::git-format-patch -O<orderfile>:: diff --git a/Documentation/gitdiffcore.txt b/Documentation/gitdiffcore.txt index 568d757..ef4c04a 100644 --- a/Documentation/gitdiffcore.txt +++ b/Documentation/gitdiffcore.txt @@ -222,26 +222,33 @@ version prefixed with '+'. diffcore-pickaxe: For Detecting Addition/Deletion of Specified String --------------------------------------------------------------------- -This transformation is used to find filepairs that represent -changes that touch a specified string, and is controlled by the --S option and the `--pickaxe-all` option to the 'git diff-*' -commands. - -When diffcore-pickaxe is in use, it checks if there are -filepairs whose "result" side and whose "origin" side have -different number of specified string. Such a filepair represents -"the string appeared in this changeset". It also checks for the -opposite case that loses the specified string. - -When `--pickaxe-all` is not in effect, diffcore-pickaxe leaves -only such filepairs that touch the specified string in its -output. When `--pickaxe-all` is used, diffcore-pickaxe leaves all -filepairs intact if there is such a filepair, or makes the -output empty otherwise. The latter behaviour is designed to -make reviewing of the changes in the context of the whole +There are two kinds of pickaxe: the S kind (corresponding to 'git log +-S') and the G kind (mnemonic: grep; corresponding to 'git log -G'). + +"-S<block of text>" detects filepairs whose preimage and postimage +have different number of occurrences of the specified block of text. +By definition, it will not detect in-file moves. Also, when a +changeset moves a file wholesale without affecting the interesting +string, rename detection kicks in as usual, and `-S` omits the +filepair (since the number of occurrences of that string didn't change +in that rename-detected filepair). The implementation essentially +runs a count, and is significantly cheaper than the G kind. When used +with `--pickaxe-regex`, treat the <block of text> as an extended POSIX +regular expression to match, instead of a literal string. + +"-G<regular expression>" detects filepairs whose textual diff has an +added or a deleted line that matches the given regular expression. +This means that it can detect in-file (or what rename-detection +considers the same file) moves. The implementation runs diff twice +and greps, and this can be quite expensive. + +When `-S` or `-G` are used without `--pickaxe-all`, only filepairs +that match their respective criterion are kept in the output. When +`--pickaxe-all` is used, if even one filepair matches their respective +criterion in a changeset, the entire changeset is kept. This behavior +is designed to make reviewing changes in the context of the whole changeset easier. - diffcore-order: For Sorting the Output Based on Filenames --------------------------------------------------------- -- 1.8.3.rc3.17.gd95ec6c.dirty -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html