[PATCH v7 2/3] Documentation: alias: add notes on shell expansion

Ian Wienand
2024-05-27T00:32:22Z

When writing inline shell for shell-expansion aliases (i.e. prefixed
with "!"), there are some caveats around argument parsing to be aware
of. This series of notes attempts to explain what is happening more
clearly.

Signed-off-by: Ian Wienand <iwienand@redhat.com>
---
Documentation/config/alias.txt | 14 ++++++++++++++
1 file changed, 14 insertions(+)

diff --git a/Documentation/config/alias.txt b/Documentation/config/alias.txt
index 40851ef429..75f9f5e26f 100644
--- a/Documentation/config/alias.txt
+++ b/Documentation/config/alias.txt
@@ -27,3 +27,17 @@ it will be treated as a shell command. For example, defining
repository, which may not necessarily be the current directory.
* `GIT_PREFIX` is set as returned by running `git rev-parse --show-prefix`
from the original current directory. See linkgit:git-rev-parse[1].
+* Shell command aliases always receive any extra arguments provided to
+ the Git command-line as positional arguments.
+** Care should be taken if your shell alias is a "one-liner" script
+ with multiple commands (e.g. in a pipeline), references multiple
+ arguments, or is otherwise not able to handle positional arguments
+ appended via `"$@"`. For example: `alias.cmd = "!echo $1 | grep
+ $2"` called as `git cmd 1 2` will be executed as 'echo $1 | grep $2
+ 1 2', which is not what you want.
+** A convenient way to deal with this is to write your script
+ operations in an inline function that is then called with any
+ arguments from the command-line. For example `alias.cmd = "!c() {
+ echo $1 | grep $2 ; }; c" will correctly execute the prior example.
+** Setting `GIT_TRACE=1` can help you debug the command being run for
+ your alias.
--
2.45.1