[PATCH] Give support for hooks based on platform

From: rafael-santiago <redacted>

The idea behind this commit can be useful for teams
that share git-hooks into a custom directory and
dealing with projects that must be developed,
built, maintained on several different platforms.

This commit allows the execution of git hooks
based on the current operating system.
A "native hook" is defined in the form:
    hooks/hook-name_platform
Where platform must be equivalent to the
content returned in sysname field in utsname
struct when calling uname() [but all normalized
in lowercase].

On Windows, independent of version, flavor, SP,
whatever it is simply "windows".

When a native hook is not found the standard
hook (.git/hook/hook-name), if found is executed,
of course. In other words, the hook without a
platform postfix (_yyz) is the standard hook.
When native hook is not set as executable but
standard is set, the standard will be executed.

The main motivation of this extension is to
reduce dependency of scripting languages,
logical trinkets etc just to execute minor
tasks during scm events that could be done
natively but differently from a platform
to another. Less dependencies, cleaner
repos: a small step for a better world
for any software developer.

Signed-off-by: Rafael Santiago <redacted>
---
    Give support for hooks based on platform
    
    The idea behind this commit can be useful for teams that share git-hooks
    into a custom directory and dealing with projects that must be
    developed, built, maintained on several different platforms.
    
    This commit allows the execution of git hooks based on the current
    operating system. A "native hook" is defined in the form:
    hooks/hook-name_platform
    
    Where platform must be equivalent to the content returned in sysname
    field in utsname struct when calling uname() [but all normalized in
    lowercase].
    
    On Windows, independent of version, flavor, SP, whatever it is simply
    "windows".
    
    When a native hook is not found the standard hook (.git/hook/hook-name),
    if found is executed, of course. In other words, the hook without a
    platform postfix (_yyz) is the standard hook. When native hook is not
    set as executable but standard is set, the standard will be executed.
    
    The main motivation of this extension is to reduce dependency of
    scripting languages, logical trinkets etc just to execute minor tasks
    during scm events that could be done natively but differently from a
    platform to another. Less dependencies, cleaner repos: a small step for
    a better world for any software developer.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1069%2Frafael-santiago%2Fmaster-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1069/rafael-santiago/master-v1
Pull-Request: https://github.com/git/git/pull/1069

 run-command.c                     | 41 ++++++++++++++++++++
 t/t7527-pre-commit-native-hook.sh | 63 +++++++++++++++++++++++++++++++
 2 files changed, 104 insertions(+)
 create mode 100755 t/t7527-pre-commit-native-hook.sh

diff --git a/run-command.c b/run-command.c
index f72e72cce73..973c1a3434b 100644
--- a/run-command.c
+++ b/run-command.c

@@ -1319,9 +1319,50 @@ int async_with_fork(void)
 #endif
 }
 
+static inline const char *platform_name(void)
+{
+	static const char *platform = NULL;
+#ifndef GIT_WINDOWS_NATIVE
+	static struct utsname un = { 0 };
+#endif
+	if (platform != NULL)
+		return platform;
+
+#ifndef GIT_WINDOWS_NATIVE
+	if (uname(&un) == 0) {
+		for (size_t s = 0; un.sysname[s] != 0; s++)
+			un.sysname[s] = tolower(un.sysname[s]);
+		platform = un.sysname;
+	}
+#else
+    platform = "windows";
+#endif
+
+    return platform;
+}
+
+static const char *find_native_hook(const char *name)
+{
+	char native_name[64] = "";
+	const char *platform = NULL;
+	if (name == NULL || strstr(name, "_") != NULL)
+		return NULL;
+
+	platform = platform_name();
+	if (platform == NULL)
+		return NULL;
+
+	if (snprintf(native_name, sizeof(native_name) - 1, "%s_%s", name, platform) >= sizeof(native_name) - 1)
+		return NULL;
+	return find_hook(native_name);
+}
+
 const char *find_hook(const char *name)
 {
+	const char *native_hook = find_native_hook(name);
 	static struct strbuf path = STRBUF_INIT;
+	if (native_hook != NULL)
+		return native_hook;
 
 	strbuf_reset(&path);
 	strbuf_git_path(&path, "hooks/%s", name);

diff --git a/t/t7527-pre-commit-native-hook.sh b/t/t7527-pre-commit-native-hook.sh
new file mode 100755
index 00000000000..f3835f943af
--- /dev/null
+++ b/t/t7527-pre-commit-native-hook.sh

@@ -0,0 +1,63 @@
+#!/bin/sh
+
+test_description='Test native hooks extension'
+
+. ./test-lib.sh
+
+expected_platform=$(uname -s | tr A-Z a-z)
+
+if [ $(expr substr $(uname -s | tr A-Z a-z) 1 5) == "mingw" ] ; then
+    expected_platform="windows"
+fi
+
+test_expect_success 'set standard and native pre-commit hooks' '
+	mkdir -p test-repo &&
+	cd test-repo &&
+	git init &&
+	mkdir -p .git/hooks &&
+	echo \#!/bin/sh > .git/hooks/pre-commit &&
+	echo echo Hello generic. >> .git/hooks/pre-commit &&
+	chmod u+x .git/hooks/pre-commit &&
+	echo \#!/bin/sh > .git/hooks/pre-commit_${expected_platform} &&
+	echo echo Hello ${expected_platform} >> .git/hooks/pre-commit_${expected_platform} &&
+	chmod u+x .git/hooks/pre-commit_${expected_platform} &&
+	echo test > README &&
+	git add README &&
+	git commit -am "1-2-3 this is a test." 2>out.txt &&
+	cat out.txt | grep Hello\ ${expected_platform}
+'
+
+if [ ${expected_platform} != "windows" ] ; then
+	# chmod does not work well on Windows.
+	test_expect_success 'set standard and native pre-commit hooks but let the native one not executable' '
+		mkdir -p test-repo &&
+		cd test-repo &&
+		git init &&
+		mkdir -p .git/hooks &&
+		echo \#!/bin/sh > .git/hooks/pre-commit &&
+		echo echo Hello generic. >> .git/hooks/pre-commit &&
+		chmod u+x .git/hooks/pre-commit &&
+		echo \#!/bin/sh > .git/hooks/pre-commit_${expected_platform} &&
+		echo echo Hello ${expected_platform} >> .git/hooks/pre-commit_${expected_platform} &&
+		echo test > README &&
+		git add README &&
+		git commit -am "1-2-3 this is a test." 2>out.txt &&
+		cat out.txt | grep Hello\ generic
+	'
+
+	test_expect_success 'set standard pre-commit hook only' '
+		mkdir -p test-repo &&
+		cd test-repo &&
+		git init &&
+		mkdir -p .git/hooks &&
+		echo \#!/bin/sh > .git/hooks/pre-commit &&
+		echo echo Hello standard hook. >> .git/hooks/pre-commit &&
+		chmod u+x .git/hooks/pre-commit &&
+		echo test > README &&
+		git add README &&
+		git commit -am "1-2-3 this is a test." 2>out.txt &&
+		cat out.txt | grep Hello\ standard\ hook
+	'
+fi
+
+test_done

base-commit: 225bc32a989d7a22fa6addafd4ce7dcd04675dbf
-- 
gitgitgadget

On 2021-08-21 at 20:00:07, Rafael Santiago via GitGitGadget wrote:

From: rafael-santiago <redacted>

The idea behind this commit can be useful for teams
that share git-hooks into a custom directory and
dealing with projects that must be developed,
built, maintained on several different platforms.

This commit allows the execution of git hooks
based on the current operating system.
A "native hook" is defined in the form:
    hooks/hook-name_platform
Where platform must be equivalent to the
content returned in sysname field in utsname
struct when calling uname() [but all normalized
in lowercase].

On Windows, independent of version, flavor, SP,
whatever it is simply "windows".

I'm not sure that this is going to work out very well.  The MINGW
environment used by Git for Windows and Cygwin are quite different.  I
would fully expect to write shell scripts and Unix tooling in Cygwin,
whereas users using Git for Windows might not want that at all.  That
also doesn't take into effect using Git for Windows in WSL, which
introduces some interesting logistical challenges.

In addition, I have a few concerns about the grouping of Linux
altogether.  While in many cases it is possible to write tooling that
works natively across Linux distros, most binaries will not.  Therefore,
binary hooks that might run fine on Debian would fail on a Fedora or Red
Hat system, especially if those binaries link to any of a number of
different shared libraries (e.g., OpenSSL).

There's also work to move hooks into the config and out of the hooks
directory, and I don't think this will mesh well with it.

The main motivation of this extension is to
reduce dependency of scripting languages,
logical trinkets etc just to execute minor
tasks during scm events that could be done
natively but differently from a platform
to another. Less dependencies, cleaner
repos: a small step for a better world
for any software developer.

Is there a reason that the proper hooks couldn't be copied or symlinked
into place with a script?  I think that would resolve this concern with
a lot less work.
-- 
brian m. carlson (he/him or they/them)
Toronto, Ontario, CA

In my opinion "binary hooks" (hooks that execute specific binaries not present in the system as a default tool) should be versioned and built as a support tool into the repository or in the worst case downloaded from somewhere, even because versioning binaries into git repos is considered a bad practice that could make bloated repos.

The point is that in many cases a dependency with a script language is created only to make the hook actions portable from a platform to other, but what this script in its essence does is a thing that could be done with basic tools delivered with the current operating system.

There is no problem on using cygwin on windows, you should use standard hook and do all the effort to make it unique for cygwin environments and true unix boxes (in other words: you would continue doing what you are doing, because it attends yours requirements). Notice that everything that have been working will stay working as before. Anyway, if cygwin becomes a point of incompatibility at some point, you could use the "_windows" version by coding your "cygwin script" there.
Maybe this would add more possibilities in git-hook tooling by making them less plastered, I think.

Rafael Santiago
-- 
21 de ago. de 2021 18:50 por sandals@crustytoothpaste.net:

On 2021-08-21 at 20:00:07, Rafael Santiago via GitGitGadget wrote:

quoted

From: rafael-santiago <redacted>

The idea behind this commit can be useful for teams
that share git-hooks into a custom directory and
dealing with projects that must be developed,
built, maintained on several different platforms.

This commit allows the execution of git hooks
based on the current operating system.
A "native hook" is defined in the form:
 hooks/hook-name_platform
Where platform must be equivalent to the
content returned in sysname field in utsname
struct when calling uname() [but all normalized
in lowercase].

On Windows, independent of version, flavor, SP,
whatever it is simply "windows".

I'm not sure that this is going to work out very well.  The MINGW
environment used by Git for Windows and Cygwin are quite different.  I
would fully expect to write shell scripts and Unix tooling in Cygwin,
whereas users using Git for Windows might not want that at all.  That
also doesn't take into effect using Git for Windows in WSL, which
introduces some interesting logistical challenges.

In addition, I have a few concerns about the grouping of Linux
altogether.  While in many cases it is possible to write tooling that
works natively across Linux distros, most binaries will not.  Therefore,
binary hooks that might run fine on Debian would fail on a Fedora or Red
Hat system, especially if those binaries link to any of a number of
different shared libraries (e.g., OpenSSL).

There's also work to move hooks into the config and out of the hooks
directory, and I don't think this will mesh well with it.

quoted

The main motivation of this extension is to
reduce dependency of scripting languages,
logical trinkets etc just to execute minor
tasks during scm events that could be done
natively but differently from a platform
to another. Less dependencies, cleaner
repos: a small step for a better world
for any software developer.

Is there a reason that the proper hooks couldn't be copied or symlinked
into place with a script?  I think that would resolve this concern with
a lot less work.
-- 
brian m. carlson (he/him or they/them)
Toronto, Ontario, CA

On 2021-08-21 at 23:11:27, Rafael Santiago wrote:

In my opinion "binary hooks" (hooks that execute specific binaries not
present in the system as a default tool) should be versioned and built
as a support tool into the repository or in the worst case downloaded
from somewhere, even because versioning binaries into git repos is
considered a bad practice that could make bloated repos.

Yes, I agree binary hooks should not be checked into the repository.

The point is that in many cases a dependency with a script language is
created only to make the hook actions portable from a platform to
other, but what this script in its essence does is a thing that could
be done with basic tools delivered with the current operating system.

Then, in general, it can be done in a shell script containing an if-then
statement per platform using the native tools, so I'm not seeing the
particular reason that this series is necessary if the hooks being
executed aren't binaries.  All systems on which Git runs must contain a
POSIX-compatible shell.

Can you explain the rationale for your proposal in more detail so that
we can understand why this change is necessary?  Typically this is done
in the commit message, but I don't think I understand why you want to do
this.

There is no problem on using cygwin on windows, you should use
standard hook and do all the effort to make it unique for cygwin
environments and true unix boxes (in other words: you would continue
doing what you are doing, because it attends yours requirements).
Notice that everything that have been working will stay working as
before. Anyway, if cygwin becomes a point of incompatibility at some
point, you could use the "_windows" version by coding your "cygwin
script" there.

Right, my point is that your commit message proposes using "windows" for
Cygwin.  The patch doesn't, but your commit message says that every
version of Windows is considered "windows".
-- 
brian m. carlson (he/him or they/them)
Toronto, Ontario, CA

Well, you are taking into consideration that every git user that needs to
automate some stuff during a scm event will do it from a shell
(I meant true shell or a mocked up one such as cygwin, msys, etc)
and it is true, by design.

However, not all git users (out unix) uses git from "bash-like"
environments. I know people that prefers using it from a well-cooked
IDE by clicking and dragging things or even from command prompt when
on Windows. Those people are not able to handle some scm event
automation as unix users because git hook in its essence presupposes
the existence/necessity of a powerful shell (okay, it is possible to
put a shebang and call a batch file on windows, maybe, but it is a
little clumsy, in my opinion). On Windows, users can do a bunch of stuff
just by using the ready to go powershell, but open an if/else on a bash
script to run a cygwin instance by calling powershell from there is not a
good and clean solution for this type of user. Presupposing shell for git,
limitates the idea behind the scm event handling with hooks, because
currently it is strongly dependent from shell to work on every git
supported platform.

The idea of having hooks being executed by platform would be the first
step to give support to execute commands on scm events without
obligating users out of a unix have a shell interpreter to access
native stuff. Currently, this commit does not implement it but would be
possible to do and in a  less noisy way for all unix-like stuff. I am not sure
but currently a _windows hook out from cygwin would result on a spawn
error, would not?

Git hooks are useful features but would be more useful if it breaked up
the shell jail. It could make git much more integrated with the current
platform.  Being possible to make it powerful as it is on a unix even on
a total different platform as Windows, let's say.

For sure, this commit are not a "panacea" but intends to start making
git-hooks more independent from 3rd party software to work on as expected,
on every platform that a git-repo is expected to be handled.

I hope I was clearer from this time.

Rafael Santiago
--
22 de ago. de 2021 19:07 por sandals@crustytoothpaste.net:

On 2021-08-21 at 23:11:27, Rafael Santiago wrote:

quoted

In my opinion "binary hooks" (hooks that execute specific binaries not
present in the system as a default tool) should be versioned and built
as a support tool into the repository or in the worst case downloaded
from somewhere, even because versioning binaries into git repos is
considered a bad practice that could make bloated repos.

Yes, I agree binary hooks should not be checked into the repository.

quoted

The point is that in many cases a dependency with a script language is
created only to make the hook actions portable from a platform to
other, but what this script in its essence does is a thing that could
be done with basic tools delivered with the current operating system.

Then, in general, it can be done in a shell script containing an if-then
statement per platform using the native tools, so I'm not seeing the
particular reason that this series is necessary if the hooks being
executed aren't binaries.  All systems on which Git runs must contain a
POSIX-compatible shell.

Can you explain the rationale for your proposal in more detail so that
we can understand why this change is necessary?  Typically this is done
in the commit message, but I don't think I understand why you want to do
this.

quoted

There is no problem on using cygwin on windows, you should use
standard hook and do all the effort to make it unique for cygwin
environments and true unix boxes (in other words: you would continue
doing what you are doing, because it attends yours requirements).
Notice that everything that have been working will stay working as
before. Anyway, if cygwin becomes a point of incompatibility at some
point, you could use the "_windows" version by coding your "cygwin
script" there.

Right, my point is that your commit message proposes using "windows" for
Cygwin.  The patch doesn't, but your commit message says that every
version of Windows is considered "windows".
-- 
brian m. carlson (he/him or they/them)
Toronto, Ontario, CA

On Sun, Aug 22, 2021 at 10:07:41PM +0000, brian m. carlson wrote:

quoted

The point is that in many cases a dependency with a script language is
created only to make the hook actions portable from a platform to
other, but what this script in its essence does is a thing that could
be done with basic tools delivered with the current operating system.

Then, in general, it can be done in a shell script containing an if-then
statement per platform using the native tools, so I'm not seeing the
particular reason that this series is necessary if the hooks being
executed aren't binaries.  All systems on which Git runs must contain a
POSIX-compatible shell.

This is my gut feeling, too (whether users know it or not, even on
Windows most programs specified by config are being run by the shell).

However, I do think there is room for Git to make this case a bit
easier: conditional config includes. Once we are able to specify hooks
via config (which is being worked on elsewhere), then we ought to be
able to implement an includeIf like:

  [includeIf "uname_s:linux"]
  path = linux-hooks.config
  [includeIf "uname_s:windows"]
  path = windows-hooks.config

The advantage being that this could apply to _all_ config, and not just
hooks.

It may still require fighting over which values should match on cygwin. ;)

-Peff