feat(vimscript): scripts can detect 'android', 'termux' #38218

Problem:
The 'android' and 'termux' feature flags have been shipped in the
downstream neovim/neovim-nightly package for 5+ years but were never
properly documented in the downstream patch.

Solution:
Upstream the 'android' and 'termux' feature flags into Neovim as
decoupled feature flags, this enables the 'android' feature in
particular to be available independently of the 'termux' feature
for builds of Neovim against the Android NDK, but not including
the Termux NDK patchset.

Co-authored-by: Lethal Lisa <43791059+lethal-lisa@users.noreply.github.com>
Co-authored-by: shadmansaleh <13149513+shadmansaleh@users.noreply.github.com>

runtime/doc/news.txt

@@ -464,6 +464,7 @@ VIMSCRIPT
 • |chdir()| allows optionally specifying a scope argument.
 • |cmdcomplete_info()| gets current cmdline completion info.
 • |getcompletiontype()| gets command-line completion type for any string.
+• |has()| gained two new system dependent feature flags, |android| and |termux|.
 • |prompt_getinput()| gets current user-input in prompt-buffer.
 • |wildtrigger()| triggers command-line expansion.
 • |v:vim_did_init| is set after sourcing |init.vim| but before |load-plugins|.

runtime/doc/vimfn.txt

@@ -4689,6 +4689,7 @@ has({feature})                                                           *has()*
 <							*feature-list*
 		    List of supported pseudo-feature names:
 			acl		|ACL| support.
+			*android*	Android system (not necessarily |termux|).
 			bsd		BSD system (not macOS, use "mac" for that).
 			clipboard	|clipboard| provider is available.
 			fname_case	Case in file names matters (for Darwin and MS-Windows
@@ -4702,6 +4703,7 @@ has({feature})                                                           *has()*
 			python3		Legacy Vim |python3| interface. |has-python|
 			pythonx		Legacy Vim |python_x| interface. |has-pythonx|
 			sun		SunOS system.
+			*termux*	Termux, an |android| terminal app and packaging environment.
 			ttyin		input is a terminal (tty).
 			ttyout		output is a terminal (tty).
 			unix		Unix system.

runtime/lua/vim/_meta/vimfn.lua

@@ -4236,6 +4236,7 @@ function vim.fn.globpath(path, expr, nosuf, list, allinks) end
 --- <          *feature-list*
 ---     List of supported pseudo-feature names:
 ---   acl    |ACL| support.
+---   *android*  Android system (not necessarily |termux|).
 ---   bsd    BSD system (not macOS, use "mac" for that).
 ---   clipboard  |clipboard| provider is available.
 ---   fname_case  Case in file names matters (for Darwin and MS-Windows
@@ -4249,6 +4250,7 @@ function vim.fn.globpath(path, expr, nosuf, list, allinks) end
 ---   python3    Legacy Vim |python3| interface. |has-python|
 ---   pythonx    Legacy Vim |python_x| interface. |has-pythonx|
 ---   sun    SunOS system.
+---   *termux*  Termux, an |android| terminal app and packaging environment.
 ---   ttyin    input is a terminal (tty).
 ---   ttyout    output is a terminal (tty).
 ---   unix    Unix system.

src/nvim/eval.lua

@@ -5221,6 +5221,7 @@ M.funcs = {
       <					*feature-list*
           List of supported pseudo-feature names:
       	acl		|ACL| support.
+      	*android*	Android system (not necessarily |termux|).
       	bsd		BSD system (not macOS, use "mac" for that).
       	clipboard	|clipboard| provider is available.
       	fname_case	Case in file names matters (for Darwin and MS-Windows
@@ -5234,6 +5235,7 @@ M.funcs = {
       	python3		Legacy Vim |python3| interface. |has-python|
       	pythonx		Legacy Vim |python_x| interface. |has-pythonx|
       	sun		SunOS system.
+      	*termux*	Termux, an |android| terminal app and packaging environment.
       	ttyin		input is a terminal (tty).
       	ttyout		output is a terminal (tty).
       	unix		Unix system.

src/nvim/eval/funcs.c

@@ -2654,6 +2654,9 @@ static void f_gettext(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 static void f_has(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 {
   static const char *const has_list[] = {
+#ifdef __ANDROID__
+    "android",
+#endif
 #if defined(BSD) && !defined(__APPLE__) && !defined(__GNU__)
     "bsd",
 #endif
@@ -2666,6 +2669,9 @@ static void f_has(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 #ifdef SUN_SYSTEM
     "sun",
 #endif
+#ifdef __TERMUX__
+    "termux",
+#endif
 #ifdef UNIX
     "unix",
 #endif