From: Junio C Hamano Date: Mon, 6 Jun 2005 00:46:06 +0000 (-0700) Subject: [PATCH] Start cvs-migration documentation X-Git-Tag: v0.99~320 X-Git-Url: http://git.tremily.us/?a=commitdiff_plain;h=b0bf8f24e9c7bdeb7e472e6b1fa5f51de1cdcc97;p=git.git [PATCH] Start cvs-migration documentation This does a section to talk about "cvs annotate". Signed-off-by: Junio C Hamano Signed-off-by: Linus Torvalds --- diff --git a/Documentation/cvs-migration.txt b/Documentation/cvs-migration.txt new file mode 100644 index 000000000..146c60944 --- /dev/null +++ b/Documentation/cvs-migration.txt @@ -0,0 +1,105 @@ +CVS annotate. + +The core GIT itself does not have a "cvs annotate" equivalent. +It has something that you may want to use when you would use +"cvs annotate". + +Let's step back a bit and think about the reason why you would +want to do "cvs annotate a-file.c" to begin with. + +You would use "cvs annotate" on a file when you have trouble +with a function (or even a single "if" statement in a function) +that happens to be defined in the file, which does not do what +you want it to do. And you would want to find out why it was +written that way, because you are about to modify it to suit +your needs, and at the same time you do not want to break its +current callers. For that, you are trying to find out why the +original author did things that way in the original context. + +Many times, it may be enough to see the commit log messages of +commits that touch the file in question, possibly along with the +patches themselves, like this: + + $ git-whatchanged -p a-file.c + +This will show log messages and patches for each commit that +touches a-file. + +This, however, may not be very useful when this file has many +modifications that are not related to the piece of code you are +interested in. You would see many log messages and patches that +do not have anything to do with the piece of code you are +interested in. As an example, assuming that you have this piece +code that you are interested in in the HEAD version: + + if (frotz) { + nitfol(); + } + +you would use git-rev-list and git-diff-tree like this: + + $ git-rev-list HEAD | + git-diff-tree --stdin -v -p -S'if (frotz) { + nitfol(); + }' + +We have already talked about the "--stdin" form of git-diff-tree +command that reads the list of commits and compares each commit +with its parents. The git-whatchanged command internally runs +the equivalent of the above command, and can be used like this: + + $ git-whatchanged -p -S'if (frotz) { + nitfol(); + }' + +When the -S option is used, git-diff-tree command outputs +differences between two commits only if one tree has the +specified string in a file and the corresponding file in the +other tree does not. The above example looks for a commit that +has the "if" statement in it in a file, but its parent commit +does not have it in the same shape in the corresponding file (or +the other way around, where the parent has it and the commit +does not), and the differences between them are shown, along +with the commit message (thanks to the -v flag). It does not +show anything for commits that do not touch this "if" statement. + +Also, in the original context, the same statement might have +appeared at first in a different file and later the file was +renamed to "a-file.c". CVS annotate would not help you to go +back across such a rename, but GIT would still help you in such +a situation. For that, you can give the -C flag to +git-diff-tree, like this: + + $ git-whatchanged -p -C -S'if (frotz) { + nitfol(); + }' + +When the -C flag is used, file renames and copies are followed. +So if the "if" statement in question happens to be in "a-file.c" +in the current HEAD commit, even if the file was originally +called "o-file.c" and then renamed in an earlier commit, or if +the file was created by copying an existing "o-file.c" in an +earlier commit, you will not lose track. If the "if" statement +did not change across such rename or copy, then the commit that +does rename or copy would not show in the output, and if the +"if" statement was modified while the file was still called +"o-file.c", it would find the commit that changed the statement +when it was in "o-file.c". + +[ BTW, the current versions of "git-diff-tree -C" is not eager + enough to find copies, and it will miss the fact that a-file.c + was created by copying o-file.c unless o-file.c was somehow + changed in the same commit.] + +You can use the --pickaxe-all flag in addition to the -S flag. +This causes the differences from all the files contained in +those two commits, not just the differences between the files +that contain this changed "if" statement: + + $ git-whatchanged -p -C -S'if (frotz) { + nitfol(); + }' --pickaxe-all + +[ Side note. This option is called "--pickaxe-all" because -S + option is internally called "pickaxe", a tool for software + archaeologists.]