bisect: add the terms old/new

diff --git a/Documentation/git-bisect.txt b/Documentation/git-bisect.txt
index e97f2de21bdc58cc2de35731f7b339353b121bd0..abaf462273c1ad367474058d4abc630155e99a37 100644 (file)
--- a/Documentation/git-bisect.txt
+++ b/Documentation/git-bisect.txt
@@ -17,8 +17,8 @@ The command takes various subcommands, and different options depending
 on the subcommand:
 
  git bisect start [--no-checkout] [<bad> [<good>...]] [--] [<paths>...]
- git bisect bad [<rev>]
- git bisect good [<rev>...]
+ git bisect (bad|new) [<rev>]
+ git bisect (good|old) [<rev>...]
  git bisect skip [(<rev>|<range>)...]
  git bisect reset [<commit>]
  git bisect visualize
@@ -36,6 +36,13 @@ whether the selected commit is "good" or "bad". It continues narrowing
 down the range until it finds the exact commit that introduced the
 change.
 
+In fact, `git bisect` can be used to find the commit that changed
+*any* property of your project; e.g., the commit that fixed a bug, or
+the commit that caused a benchmark's performance to improve. To
+support this more general usage, the terms "old" and "new" can be used
+in place of "good" and "bad". See
+section "Alternate terms" below for more information.
+
 Basic bisect commands: start, bad, good
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
@@ -111,6 +118,45 @@ bad revision, while `git bisect reset HEAD` will leave you on the
 current bisection commit and avoid switching commits at all.
 
 
+Alternate terms
+~~~~~~~~~~~~~~~
+
+Sometimes you are not looking for the commit that introduced a
+breakage, but rather for a commit that caused a change between some
+other "old" state and "new" state. For example, you might be looking
+for the commit that introduced a particular fix. Or you might be
+looking for the first commit in which the source-code filenames were
+finally all converted to your company's naming standard. Or whatever.
+
+In such cases it can be very confusing to use the terms "good" and
+"bad" to refer to "the state before the change" and "the state after
+the change". So instead, you can use the terms "old" and "new",
+respectively, in place of "good" and "bad". (But note that you cannot
+mix "good" and "bad" with "old" and "new" in a single session.)
+
+In this more general usage, you provide `git bisect` with a "new"
+commit has some property and an "old" commit that doesn't have that
+property. Each time `git bisect` checks out a commit, you test if that
+commit has the property. If it does, mark the commit as "new";
+otherwise, mark it as "old". When the bisection is done, `git bisect`
+will report which commit introduced the property.
+
+To use "old" and "new" instead of "good" and bad, you must run `git
+bisect start` without commits as argument and then run the following
+commands to add the commits:
+
+------------------------------------------------
+git bisect old [<rev>]
+------------------------------------------------
+
+to indicate that a commit was before the sought change, or
+
+------------------------------------------------
+git bisect new [<rev>...]
+------------------------------------------------
+
+to indicate that it was after.
+
 Bisect visualize
 ~~~~~~~~~~~~~~~~
 
@@ -387,6 +433,14 @@ In this case, when 'git bisect run' finishes, bisect/bad will refer to a commit
 has at least one parent whose reachable graph is fully traversable in the sense
 required by 'git pack objects'.
 
+* Look for a fix instead of a regression in the code
++
+------------
+$ git bisect start
+$ git bisect new HEAD    # current commit is marked as new
+$ git bisect old HEAD~10 # the tenth commit from now is marked as old
+------------
+
 Getting help
 ~~~~~~~~~~~~