core: Add ExecSearchPath parameter to specify the directory relative to which binaries executed by Exec*= should be found

Currently there does not exist a way to specify a path relative to which
all binaries executed by Exec should be found. The only way is to
specify the absolute path.

This change implements the functionality to specify a path relative to which
binaries executed by Exec*= can be found.

Closes #6308

test/test-execute/exec-execsearchpath-environment-path-set.service

@@ -0,0 +1,5 @@
+[Service]
+ExecStart=/bin/sh -x -c 'test "$$PATH" = "/usr" && test "$$VAR1" = word3 && test "$$VAR2" = "\\$$word 5 6"'
+Type=oneshot
+ExecSearchPath=/tmp:/bin
+Environment="PATH=/usr" VAR1=word3 "VAR2=$word 5 6"

test/test-execute/exec-execsearchpath-environment.service

@@ -0,0 +1,5 @@
+[Service]
+ExecStart=/bin/sh -x -c 'test "$$VAR1" = "word1 word2" && test "$$VAR2" = word3 && test "$$VAR3" = "\\$$word 5 6" && test "$$PATH" = "/tmp:/bin"'
+Type=oneshot
+ExecSearchPath=/tmp:/bin
+Environment="VAR1=word1 word2" VAR2=word3 "VAR3=$word 5 6"

test/test-execute/exec-execsearchpath-environmentfile-set.service

@@ -0,0 +1,8 @@
+[Unit]
+Description=Test for ExecSearchPath with EnvironmentFile where EnvironmentFile sets PATH
+
+[Service]
+ExecStart=/bin/sh -x -c 'test "$$VAR1" = "word1 word2" && test "$$VAR2" = word3 && test "$$VAR3" = "\\$$word 5 6" && test "$$VAR4" = "new\nline" && test "$$VAR5" = passwordwithbackslashes && test "$$PATH" = /usr'
+Type=oneshot
+EnvironmentFile=/tmp/test-exec_execsearchpath_environmentfile-set.conf
+ExecSearchPath=/tmp:/bin

test/test-execute/exec-execsearchpath-environmentfile.service

@@ -0,0 +1,8 @@
+[Unit]
+Description=Test for ExecSearchPath with EnvironmentFile where EnvironmentFile does not set PATH
+
+[Service]
+ExecStart=/bin/sh -x -c 'test "$$VAR1" = "word1 word2" && test "$$VAR2" = word3 && test "$$VAR3" = "\\$$word 5 6" && test "$$VAR4" = "new\nline" && test "$$VAR5" = passwordwithbackslashes && test "$$PATH" = "/tmp:/bin"'
+Type=oneshot
+ExecSearchPath=/tmp:/bin
+EnvironmentFile=/tmp/test-exec_execsearchpath_environmentfile.conf

test/test-execute/exec-execsearchpath-passenvironment-set.service

@@ -0,0 +1,8 @@
+[Unit]
+Description=Test for PassEnvironment with ExecSearchPath with PATH set by user
+
+[Service]
+ExecStart=/bin/sh -x -c 'test "$$VAR1" = "word1 word2" && test "$$VAR2" = word3 && test "$$VAR3" = "\\$$word 5 6" && test "$$VAR4" = "new\nline" && test "$$VAR5" = passwordwithbackslashes && test "$$PATH" = "/usr"'
+Type=oneshot
+PassEnvironment=VAR1 VAR2 VAR3 VAR4 VAR5 PATH
+ExecSearchPath=/tmp:/bin

test/test-execute/exec-execsearchpath-passenvironment.service

@@ -0,0 +1,8 @@
+[Unit]
+Description=Test for PassEnvironment with ExecSearchPath with PATH not set by user
+
+[Service]
+ExecStart=/bin/sh -x -c 'test "$$VAR1" = "word1 word2" && test "$$VAR2" = word3 && test "$$VAR3" = "\\$$word 5 6" && test "$$VAR4" = "new\nline" && test "$$VAR5" = passwordwithbackslashes && test "$$PATH" = "/tmp:/bin"'
+Type=oneshot
+PassEnvironment=VAR1 VAR2 VAR3 VAR4 VAR5
+ExecSearchPath=/tmp:/bin

test/test-execute/exec-execsearchpath-unit-specifier.service

@@ -0,0 +1,7 @@
+[Unit]
+Description=Test for specifiers with exec search path
+
+[Service]
+Type=oneshot
+ExecSearchPath=/tmp:/bin:/usr/bin:%V
+ExecStart=/bin/sh -x -c 'test %V = /var/tmp && test "$$PATH" = "/tmp:/bin:/usr/bin:/var/tmp"'

test/test-execute/exec-execsearchpath.service

@@ -0,0 +1,4 @@
+[Service]
+ExecStart=ls_temp
+Type=oneshot
+ExecSearchPath=/tmp/test-exec_execsearchpath