Add the following guideline to Documentation/CodingGuidelines:
Break overlong lines after "&&", "||", and "|", not before
them; that way the command can continue to subsequent lines
without backslash at the end.
And the following to t/README (since it is specific to writing tests):
Pipes and $(git ...) should be avoided when they swallow exit
codes of Git processes
Signed-off-by: Matthew DeVore <matv...@google.com>
---
Documentation/CodingGuidelines | 18 ++++++++++++++++++
t/README | 27 +++++++++++++++++++++++++++
2 files changed, 45 insertions(+)
diff --git a/Documentation/CodingGuidelines b/Documentation/CodingGuidelines
index 48aa4edfb..72967deb7 100644
--- a/Documentation/CodingGuidelines
+++ b/Documentation/CodingGuidelines
@@ -118,6 +118,24 @@ For shell scripts specifically (not exhaustive):
do this
fi
+ - If a command sequence joined with && or || or | spans multiple
+ lines, put each command on a separate line and put && and || and |
+ operators at the end of each line, rather than the start. This
+ means you don't need to use \ to join lines, since the above
+ operators imply the sequence isn't finished.
+
+ (incorrect)
+ grep blob verify_pack_result \
+ | awk -f print_1.awk \
+ | sort >actual &&
+ ...
+
+ (correct)
+ grep blob verify_pack_result |
+ awk -f print_1.awk |
+ sort >actual &&
+ ...
+
- We prefer "test" over "[ ... ]".
- We do not write the noiseword "function" in front of shell
diff --git a/t/README b/t/README
index 68012d673..ab9fa4230 100644
--- a/t/README
+++ b/t/README
@@ -466,6 +466,33 @@ And here are the "don'ts:"
platform commands; just use '! cmd'. We are not in the business
of verifying that the world given to us sanely works.
+ - Don't feed the output of a git command to a pipe, as in:
+
+ git -C repo ls-files |
+ xargs -n 1 basename |
+ grep foo
+
+ which will discard git's exit code and may mask a crash. In the
+ above example, all exit codes are ignored except grep's.
+
+ Instead, write the output of that command to a temporary
+ file with ">" or assign it to a variable with "x=$(git ...)" rather
+ than pipe it.
+
+ - Don't use command substitution in a way that discards git's exit
+ code. When assigning to a variable, the exit code is not discarded,
+ e.g.:
+
+ x=$(git cat-file -p $sha) &&
+ ...
+
+ is OK because a crash in "git cat-file" will cause the "&&" chain
+ to fail, but:
+
+ test "refs/heads/foo" = "$(git symbolic-ref HEAD)"
+
+ is not OK and a crash in git could go undetected.
+
- Don't use perl without spelling it as "$PERL_PATH". This is to help
our friends on Windows where the platform Perl often adds CR before
the end of line, and they bundle Git with a version of Perl that
--
2.19.0.605.g01d371f741-goog
