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[203.12.11.234]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-43fb182c636sm20553761cf.52.2024.05.25.16.45.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 25 May 2024 16:45:07 -0700 (PDT) From: Ian Wienand To: git@vger.kernel.org Cc: Ian Wienand Subject: [PATCH v6 2/3] Documentation: alias: add notes on shell expansion Date: Sun, 26 May 2024 09:44:34 +1000 Message-ID: <20240525234454.1489598-2-iwienand@redhat.com> X-Mailer: git-send-email 2.45.1 In-Reply-To: <20240525234454.1489598-1-iwienand@redhat.com> References: <20240525012207.1415196-1-iwienand@redhat.com> <20240525234454.1489598-1-iwienand@redhat.com> Precedence: bulk X-Mailing-List: git@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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 --- Documentation/config/alias.txt | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) diff --git a/Documentation/config/alias.txt b/Documentation/config/alias.txt index 40851ef429..f32b86cde3 100644 --- a/Documentation/config/alias.txt +++ b/Documentation/config/alias.txt @@ -27,3 +27,31 @@ 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]. +* If the shell alias is the full path to a binary, it will be executed + directly with any arguments as positional arguments. +* If the alias contains any white-space or reserved characters, it + will be considered an inline script and run as an argument to `sh + -c`. +* When running as a script, if arguments are provided to the alias + call, Git makes them available to the process by appending "$@" to + the alias shell command. This is not appended if arguments are not + provided. +** For "simple" commands, such as calling a single binary + (e.g. `alias.myapp = !myapp --myflag1`) this will result in any + arguments becoming additional regular positional arguments to the + called binary, appended after any arguments specified in the aliased + command. +** Care should be taken if your alias script has multiple commands + (e.g. in a pipeline), references argument variables, or is + otherwise not expecting the presence of the appended `"$@"`. For + example: `alias.echo = "!echo $1"` when run as `git echo arg` will + actually execute `sh -c "echo $1 $@" "echo $1" "arg"` resulting in + output `arg arg`. When writing such aliases, you should ensure + that the appended "$@" when arguments are present does not cause + syntax errors or unintended side-effects. +** 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() { + cmd $1 | cmd $2 ; }; c" will allow you to work with separate + arguments. +** Setting `GIT_TRACE=1` can help debug the command being run.