From ae3f36dea16e51041c56ba9ed6b38380c8421816 Mon Sep 17 00:00:00 2001 From: Barret Rhoden Date: Wed, 15 May 2019 17:44:59 -0400 Subject: blame: add the ability to ignore commits and their changes Commits that make formatting changes or function renames are often not interesting when blaming a file. A user may deem such a commit as 'not interesting' and want to ignore and its changes it when assigning blame. For example, say a file has the following git history / rev-list: ---O---A---X---B---C---D---Y---E---F Commits X and Y both touch a particular line, and the other commits do not: X: "Take a third parameter" -MyFunc(1, 2); +MyFunc(1, 2, 3); Y: "Remove camelcase" -MyFunc(1, 2, 3); +my_func(1, 2, 3); git-blame will blame Y for the change. I'd like to be able to ignore Y: both the existence of the commit as well as any changes it made. This differs from -S rev-list, which specifies the list of commits to process for the blame. We would still process Y, but just don't let the blame 'stick.' This patch adds the ability for users to ignore a revision with --ignore-rev=rev, which may be repeated. They can specify a set of files of full object names of revs, e.g. SHA-1 hashes, one per line. A single file may be specified with the blame.ignoreRevFile config option or with --ignore-rev-file=file. Both the config option and the command line option may be repeated multiple times. An empty file name "" will clear the list of revs from previously processed files. Config options are processed before command line options. For a typical use case, projects will maintain the file containing revisions for commits that perform mass reformatting, and their users have the option to ignore all of the commits in that file. Additionally, a user can use the --ignore-rev option for one-off investigation. To go back to the example above, X was a substantive change to the function, but not the change the user is interested in. The user inspected X, but wanted to find the previous change to that line - perhaps a commit that introduced that function call. To make this work, we can't simply remove all ignored commits from the rev-list. We need to diff the changes introduced by Y so that we can ignore them. We let the blames get passed to Y, just like when processing normally. When Y is the target, we make sure that Y does not *keep* any blames. Any changes that Y is responsible for get passed to its parent. Note we make one pass through all of the scapegoats (parents) to attempt to pass blame normally; we don't know if we *need* to ignore the commit until we've checked all of the parents. The blame_entry will get passed up the tree until we find a commit that has a diff chunk that affects those lines. One issue is that the ignored commit *did* make some change, and there is no general solution to finding the line in the parent commit that corresponds to a given line in the ignored commit. That makes it hard to attribute a particular line within an ignored commit's diff correctly. For example, the parent of an ignored commit has this, say at line 11: commit-a 11) #include "a.h" commit-b 12) #include "b.h" Commit X, which we will ignore, swaps these lines: commit-X 11) #include "b.h" commit-X 12) #include "a.h" We can pass that blame entry to the parent, but line 11 will be attributed to commit A, even though "include b.h" came from commit B. The blame mechanism will be looking at the parent's view of the file at line number 11. ignore_blame_entry() is set up to allow alternative algorithms for guessing per-line blames. Any line that is not attributed to the parent will continue to be blamed on the ignored commit as if that commit was not ignored. Upcoming patches have the ability to detect these lines and mark them in the blame output. The existing algorithm is simple: blame each line on the corresponding line in the parent's diff chunk. Any lines beyond that stay with the target. For example, the parent of an ignored commit has this, say at line 11: commit-a 11) void new_func_1(void *x, void *y); commit-b 12) void new_func_2(void *x, void *y); commit-c 13) some_line_c commit-d 14) some_line_d After a commit 'X', we have: commit-X 11) void new_func_1(void *x, commit-X 12) void *y); commit-X 13) void new_func_2(void *x, commit-X 14) void *y); commit-c 15) some_line_c commit-d 16) some_line_d Commit X nets two additionally lines: 13 and 14. The current guess_line_blames() algorithm will not attribute these to the parent, whose diff chunk is only two lines - not four. When we ignore with the current algorithm, we get: commit-a 11) void new_func_1(void *x, commit-b 12) void *y); commit-X 13) void new_func_2(void *x, commit-X 14) void *y); commit-c 15) some_line_c commit-d 16) some_line_d Note that line 12 was blamed on B, though B was the commit for new_func_2(), not new_func_1(). Even when guess_line_blames() finds a line in the parent, it may still be incorrect. Signed-off-by: Barret Rhoden Signed-off-by: Junio C Hamano --- Documentation/blame-options.txt | 14 ++++++++++++++ Documentation/config/blame.txt | 7 +++++++ Documentation/git-blame.txt | 1 + 3 files changed, 22 insertions(+) (limited to 'Documentation') diff --git a/Documentation/blame-options.txt b/Documentation/blame-options.txt index dc41957afa..2c2d1ceb56 100644 --- a/Documentation/blame-options.txt +++ b/Documentation/blame-options.txt @@ -110,5 +110,19 @@ commit. And the default value is 40. If there are more than one `-C` options given, the argument of the last `-C` will take effect. +--ignore-rev :: + Ignore changes made by the revision when assigning blame, as if the + change never happened. Lines that were changed or added by an ignored + commit will be blamed on the previous commit that changed that line or + nearby lines. This option may be specified multiple times to ignore + more than one revision. + +--ignore-revs-file :: + Ignore revisions listed in `file`, which must be in the same format as an + `fsck.skipList`. This option may be repeated, and these files will be + processed after any files specified with the `blame.ignoreRevsFile` config + option. An empty file name, `""`, will clear the list of revs from + previously processed files. + -h:: Show help message. diff --git a/Documentation/config/blame.txt b/Documentation/config/blame.txt index 67b5c1d1e0..4da2788f30 100644 --- a/Documentation/config/blame.txt +++ b/Documentation/config/blame.txt @@ -19,3 +19,10 @@ blame.showEmail:: blame.showRoot:: Do not treat root commits as boundaries in linkgit:git-blame[1]. This option defaults to false. + +blame.ignoreRevsFile:: + Ignore revisions listed in the file, one unabbreviated object name per + line, in linkgit:git-blame[1]. Whitespace and comments beginning with + `#` are ignored. This option may be repeated multiple times. Empty + file names will reset the list of ignored revisions. This option will + be handled before the command line option `--ignore-revs-file`. diff --git a/Documentation/git-blame.txt b/Documentation/git-blame.txt index 16323eb80e..7e81541996 100644 --- a/Documentation/git-blame.txt +++ b/Documentation/git-blame.txt @@ -10,6 +10,7 @@ SYNOPSIS [verse] 'git blame' [-c] [-b] [-l] [--root] [-t] [-f] [-n] [-s] [-e] [-p] [-w] [--incremental] [-L ] [-S ] [-M] [-C] [-C] [-C] [--since=] + [--ignore-rev ] [--ignore-revs-file ] [--progress] [--abbrev=] [ | --contents | --reverse ..] [--] -- cgit v1.2.3 From 8934ac8c92a1dc805f7bbd86cbc251ade66e1161 Mon Sep 17 00:00:00 2001 From: Barret Rhoden Date: Wed, 15 May 2019 17:45:00 -0400 Subject: blame: add config options for the output of ignored or unblamable lines When ignoring commits, the commit that is blamed might not be responsible for the change, due to the inaccuracy of our heuristic. Users might want to know when a particular line has a potentially inaccurate blame. Furthermore, guess_line_blames() may fail to find any parent commit for a given line touched by an ignored commit. Those 'unblamable' lines remain blamed on an ignored commit. Users might want to know if a line is unblamable so that they do not spend time investigating a commit they know is uninteresting. This patch adds two config options to mark these two types of lines in the output of blame. The first option can identify ignored lines by specifying blame.markIgnoredLines. When this option is set, each blame line that was blamed on a commit other than the ignored commit is marked with a '?'. For example: 278b6158d6fdb (Barret Rhoden 2016-04-11 13:57:54 -0400 26) appears as: ?278b6158d6fd (Barret Rhoden 2016-04-11 13:57:54 -0400 26) where the '?' is placed before the commit, and the hash has one fewer characters. Sometimes we are unable to even guess at what ancestor commit touched a line. These lines are 'unblamable.' The second option, blame.markUnblamableLines, will mark the line with '*'. For example, say we ignore e5e8d36d04cbe, yet we are unable to blame this line on another commit: e5e8d36d04cbe (Barret Rhoden 2016-04-11 13:57:54 -0400 26) appears as: *e5e8d36d04cb (Barret Rhoden 2016-04-11 13:57:54 -0400 26) When these config options are used together, every line touched by an ignored commit will be marked with either a '?' or a '*'. Signed-off-by: Barret Rhoden Signed-off-by: Junio C Hamano --- Documentation/blame-options.txt | 7 ++++++- Documentation/config/blame.txt | 9 +++++++++ 2 files changed, 15 insertions(+), 1 deletion(-) (limited to 'Documentation') diff --git a/Documentation/blame-options.txt b/Documentation/blame-options.txt index 2c2d1ceb56..5d122db6e9 100644 --- a/Documentation/blame-options.txt +++ b/Documentation/blame-options.txt @@ -115,7 +115,12 @@ take effect. change never happened. Lines that were changed or added by an ignored commit will be blamed on the previous commit that changed that line or nearby lines. This option may be specified multiple times to ignore - more than one revision. + more than one revision. If the `blame.markIgnoredLines` config option + is set, then lines that were changed by an ignored commit and attributed to + another commit will be marked with a `?` in the blame output. If the + `blame.markUnblamableLines` config option is set, then those lines touched + by an ignored commit that we could not attribute to another revision are + marked with a '*'. --ignore-revs-file :: Ignore revisions listed in `file`, which must be in the same format as an diff --git a/Documentation/config/blame.txt b/Documentation/config/blame.txt index 4da2788f30..9468e8599c 100644 --- a/Documentation/config/blame.txt +++ b/Documentation/config/blame.txt @@ -26,3 +26,12 @@ blame.ignoreRevsFile:: `#` are ignored. This option may be repeated multiple times. Empty file names will reset the list of ignored revisions. This option will be handled before the command line option `--ignore-revs-file`. + +blame.markUnblamables:: + Mark lines that were changed by an ignored revision that we could not + attribute to another commit with a '*' in the output of + linkgit:git-blame[1]. + +blame.markIgnoredLines:: + Mark lines that were changed by an ignored revision that we attributed to + another commit with a '?' in the output of linkgit:git-blame[1]. -- cgit v1.2.3