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) Signed-off-by: Ramkumar Ramachandra <artag...@gmail.com> --- I spent some time reading the code and history to figure out what -S and -G really do. I hope I've done justice. Documentation/diff-options.txt | 35 +++++++++++++++++++++++++++------- Documentation/gitdiffcore.txt | 43 +++++++++++++++++++++++------------------- 2 files changed, 52 insertions(+), 26 deletions(-) diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt index 104579d..765abc5 100644 --- a/Documentation/diff-options.txt +++ b/Documentation/diff-options.txt @@ -383,14 +383,35 @@ 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 commits where the specified string was added or + removed. More precisely, find commits that change the number + of occurrences of the specified string. ++ +It is often useful when you're looking for an exact string (like a +function prototype), and want to know the history of that string since +it first came into being. -G<regex>:: - Look for differences whose added or removed line matches - the given <regex>. + Grep through the patch text of commits for added/removed lines + that match <regex>. `--pickaxe-regex` is implied in this + mode. ++ +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 didn't 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 @@ -399,7 +420,7 @@ ifndef::git-format-patch --pickaxe-regex:: Make the <string> not a plain string but an extended POSIX - regex to match. + regex to match. Implied when using `-G`. endif::git-format-patch -O<orderfile>:: diff --git a/Documentation/gitdiffcore.txt b/Documentation/gitdiffcore.txt index 568d757..39b9c51 100644 --- a/Documentation/gitdiffcore.txt +++ b/Documentation/gitdiffcore.txt @@ -222,25 +222,30 @@ 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 -changeset easier. - +There are two kinds of pickaxe: the S kind (corresponding to 'git log +-S') and the G kind (corresponding to 'git log -G'). + +The S kind detects filepairs whose "result" side and "origin" side +have different number of occurrences of specified string. While +rename detection works as usual, 'git log -S' cannot omit commits +where a the small string being looked for is moved verbatim from one +file to another (since the number of occurrences of that string +changed in each of those two filepairs). The implementation +essentially runs a count, and is significantly cheaper than the G +kind. + +The G kind detects filepairs whose patch text has an added or a +deleted line that matches the given regexp. This means that it can +detect in-file (or what rename-detection considers the same file) +moves. The implementation of 'git log -G' runs diff twice and greps, +and this can be quite expensive. + +A diffcore-pickaxe option worth mentioning: `--pickaxe-all`. When not +in effect, diffcore-pickaxe leaves only such filepairs that touch the +specified string in its output. When in effect, diffcore-pickaxe +leaves all filepairs intact if there is such a filepair, or makes the +output empty otherwise. The latter behavior is designed to make +reviewing of the changes in the context of the whole changeset easier. diffcore-order: For Sorting the Output Based on Filenames --------------------------------------------------------- -- 1.8.3.rc1.61.g2cacfff -- 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