The git-blame(1) man page says that the .. range specifier can be used to exclude changes "older than" a certain revision. It goes on to say that it collapses all lines "not changed since the range boundary" into the boundary revision. This is the same thing --since=<rev-date> would do, and the man page even uses .. and --since in parallel as if to imply that they're alternative means of achieving the same output.
In fact, this isn't true! On the git-rev-list(1) and gitrevisions(7) man pages, it's explained that the .. specifier excludes all ancestors of the commit, not all commits on an earlier date. 'blame' is not an exception to this behavior; it uses the same functions as other commands to parse a specifier and build a revision set. If you execute: ---- #!/bin/sh mkdir blame-test pushd blame-test git init echo "line added at root" > foo echo "another line added at root" >> foo git add foo git commit -am "#1 chronologically" git checkout -b side sed '2i\ line added only on side branch ' foo > bar mv bar foo git commit -am "#2 chronologically" git checkout master echo "line added only on master branch" >> foo git commit -am "#3 chronologically" git tag boundary git merge side -m "#4 chronologically" git blame boundary.. foo popd blame-test ---- then you'll see that 'blame' treats the range specifier as 'rev-list' would: the second line is attributed to a commit which occured chronologically before `boundary`. (I guess a case could be made for an off-kilter interpretation of the phrasing, under which "since the range boundary" includes any commits not yet known to that boundary. But that would contradict the use of "since" as the name of the other limiting option, which *does* perform an absolute time cutoff.) There is at least one porcelain in fairly wide use which takes this passage of the manual at its word, so I'm not the only one who finds it confusing. I think the phrasing in the following patch is both clearer and more accurate. Signed-off-by: Daniel Koning <d...@danielkoning.com> --- Documentation/git-blame.txt | 32 ++++++++++++++++++++------------ 1 file changed, 20 insertions(+), 12 deletions(-) diff --git a/Documentation/git-blame.txt b/Documentation/git-blame.txt index 16323eb80e..91f3184e56 100644 --- a/Documentation/git-blame.txt +++ b/Documentation/git-blame.txt @@ -152,18 +152,26 @@ Also you can use a regular expression to specify the line range: which limits the annotation to the body of the `hello` subroutine. -When you are not interested in changes older than version -v2.6.18, or changes older than 3 weeks, you can use revision -range specifiers similar to 'git rev-list': - - git blame v2.6.18.. -- foo - git blame --since=3.weeks -- foo - -When revision range specifiers are used to limit the annotation, -lines that have not changed since the range boundary (either the -commit v2.6.18 or the most recent commit that is more than 3 -weeks old in the above example) are blamed for that range -boundary commit. +When you are only interested in recent changes, you can use revision +range specifiers and limiting options, just as with 'git rev-list'. + +You can limit the annotation to commits from the past 3 weeks: + + git blame --since=3.weeks -- foo + +The oldest commit in that span of time will be given the blame for any +lines that have not changed since. + +Or you can limit the annotation to commits that are not ancestors of +v2.6.18: + + git blame v2.6.18.. -- foo + +Unlike the --since option, the two-dot range specifier does not perform +a date-based cutoff. If changes from branch `fix` were merged in after +v2.6.18, the commits on `fix` which introduced those changes will appear +in the output of 'git blame', even if those commits took place at an +earlier time than v2.6.18. A particularly useful way is to see if an added file has lines created by copy-and-paste from existing files. Sometimes this -- 2.20.1